Issued 14 November 2023

October 2023 Palmer Z-Index
U.S. Percent Area Wet or Dry January 1996 - October 2023
October 2023 /monitoring-content/sotc/drought/2023/10/la-p-reg016dv00elem01-05102023.gif

Please note that the values presented in this report are based on preliminary data. They will change when the final data are processed, but will not be replaced on these pages.

National Drought Highlights

Detailed Drought Overview

The upper-level atmospheric circulation over North America during October 2023 was characterized by several high-amplitude ridges alternating with high-amplitude troughs or strong closed lows moving in the westerly jet stream flow. The troughs and closed lows sent cold fronts across the CONUS which brought episodes of cold weather. The migrating ridges spread warm weather north across the country. When averaged over the month, the mean circulation averaged out to a westerly zonal flow with a tendency for ridging in the West and troughing along the East Coast. This resulted in near- to warmer-than-normal monthly temperatures for most of the CONUS with some near- to cooler-than-normal monthly temperatures in the northern High Plains and along the Southeast Coast. The cold fronts and their associated surface lows also brought precipitation, with the month ending up wetter than normal from parts of the northern Rockies to Great Lakes and across parts of the southern Plains and New England. Moisture from the remnants of Hurricane Norma contributed to the southern Plains rainfall. But the migrating ridges, the overall westerly flow, and the preponderance of dry air masses resulted in a drier-than-normal month for much of the West, from the Lower Mississippi Valley to East Coast, and parts of the central and northern Plains and Ohio Valley. Ridging in the Pacific kept Hawaii drier than normal. October was drier than normal over southwestern parts of Alaska and northwestern Puerto Rico, but beneficial precipitation fell over other parts of Alaska, Puerto Rico, and the U.S. Virgin Islands.

The above-normal precipitation in October resulted in contraction or reduction of the intensity of drought over parts of the Pacific Northwest, Plains, Midwest, Puerto Rico, and the U.S. Virgin Islands. Drought or abnormal dryness intensified or expanded from the Lower Mississippi Valley to Mid-Atlantic Coast, in parts of the Southwest, and across much of Hawaii. Drought contraction exceeded expansion with the USDM-based national moderate-to-exceptional drought footprint across the CONUS decreasing from 40.1% at the end of September to 36.5% at the end of October (from 33.6% to 30.7% for the 50 states and Puerto Rico).

According to the Palmer Drought Index, which goes back to the beginning of the 20th century, about 29.5% of the CONUS was in moderate to extreme drought at the end of October, which is a decrease compared to the end of September.

D0-D4D1-D4D2-D4D3-D4D4

Drought conditions at the end of October, as depicted on the October 31, 2023 USDM map, included the following core drought and abnormally dry areas:

October 2023 /monitoring-content/sotc/drought/2023/10/20231031_usdm.png

Palmer Drought Index

The Palmer drought indices measure the balance between moisture demand (evapotranspiration driven by temperature) and moisture supply (precipitation). The Palmer Z Index depicts moisture conditions for the current month, while the Palmer Hydrological Drought Index (PHDI) and Palmer Drought Severity Index (PDSI) depict the current month's cumulative moisture conditions integrated over the last several months.

While both the PDSI and PHDI indices show long-term moisture conditions, the PDSI depicts meteorological drought while the PHDI depicts hydrological drought. The PDSI map may show less severe and extensive drought (as well as wet spell conditions) in some parts of the country than the PHDI map because the meteorological conditions that produce drought and wet spell conditions are not as long-lasting as the hydrological impacts.

October 2023 Palmer Z-Index
October 2023 PHDI

Used together, the Palmer Z Index and PHDI maps show that short-term drought occurred in the Southwest, southern Florida, and Lower Mississippi Valley to Mid-Atlantic states, expanding or intensifying long-term drought and reducing areas of long-term wet conditions (PHDI maps for October compared to September). Short-term wet conditions occurred in the northern Rockies, northern Plains, western Great Lakes, and northern New England, and in parts of the southern Plains, intensifying or expanding long-term wet conditions and contracting or reducing the intensity of long-term drought.

Standardized Precipitation Index

The Standardized Precipitation Index (SPI) measures moisture supply. The SPI maps here show the spatial extent of anomalously wet and dry areas at time scales ranging from 1 month to 24 months.

October 2023 SPI
September-October 2023 SPI
August-October 2023 SPI
May-October 2023 SPI

The SPI maps illustrate how moisture conditions have varied considerably through time and space over the last two years. Dryness is evident from the Lower Mississippi Valley to Mid-Atlantic Coast at the 1-month time scale, and extends from there northward into the Ohio Valley and east and west along the Gulf Coast at 2-6 months. Dry conditions continue in the Lower Mississippi Valley, along the Gulf of Mexico Coast, and in the Mid-Atlantic at 9-24 months. There is dryness in parts of the central Plains at the 2- and 3-month time scales, and this dryness extends into the Ohio and Mississippi Valleys at 6-24 months, but most especially at the 6-month time scale. Parts of the Southwest and Pacific Northwest are dry at all time scales. Parts of the southern Plains are dry at 2-12 months, with most of the southern to central Plains dry at 24 months. Much of the West (especially from California to southern Montana) and much of the Northeast are wet at all time scales; western and northern parts of the Great Plains are wet at 1- to 12-month time scales with northern parts of the Plains wet at 24 months; and wet conditions cover parts of the coastal Southeast at 6-12 months.

February-October 2023 SPI
November 2022-October 2023 SPI
November 2021-October 2023 SPI

Standardized Precipitation Evapotranspiration Index

The SPI measures water supply (precipitation), while the SPEI (Standardized Precipitation Evapotranspiration Index) measures the combination of water supply (precipitation) and water demand (evapotranspiration as computed from temperature). Warmer temperatures tend to increase evapotranspiration, which generally makes droughts more intense.

For the Northern Hemisphere, October marks the middle of climatological autumn, which is the season when a lower sun angle results in decreasing evapotranspiration. During October 2023, temperatures were still warmer than normal across most of the CONUS, with much warmer-than-average temperatures in the Southwest and Northeast and record warmth occurring in northern parts of New England. Drier-than-normal weather occurred from the Lower Mississippi Valley to Mid-Atlantic Coast, where temperatures were warmer than normal but not excessively so, and in the Southwest where temperatures were much warmer than normal. The October 2023 1-month SPEI showed much more extreme drought in the Southwest than the corresponding SPI. The SPEI was also more extreme than the SPI from the Lower Mississippi Valley to Mid-Atlantic Coast, but the difference was not as great as in the Southwest. Excessive to record warmth occurred for much of the year in the southern states (state temperature rank maps for the last 3, 6, 10 months). The resulting increased evapotranspiration resulted in SPEI values that were more extreme than the corresponding SPI values in the Southwest to central Gulf Coast (SPEI maps for the last 1, 2, 3, 6, 9, 12 months) (SPI maps for the last 1, 2, 3, 6, 9, 12 months).

The SPEI at the 1- to 9-month time scales was more extreme than the SPI for Louisiana, Arizona, and New Mexico. In some cases, the SPEI was record dry whereas the SPI was not:

The last 1 to 6 years have been unusually warm across much of the CONUS, especially in the South and West (state rank temperature maps for the last 1, 3, 4, 5 years). The last 2 to 3 years have been extremely dry in the central Plains — so dry, in fact, that the SPI is more extreme than the corresponding SPEI in spite of temperatures being above normal — but in the southern Plains the heat dominated the dryness, so the SPEI is more extreme than the SPI there (24-month SPEI, SPI) (36-month SPEI, SPI). In the western U.S., where drought has dominated for much of the last 20 years, the combination of excessive heat and dryness has resulted in more extreme SPEI values than SPI values in parts of the West for the last 2 to 6 years (SPEI maps for last 24, 36, 48, 60, 72 months) (SPI maps for last 24, 36, 48, 60, 72 months).

Regional Discussion

Mississippi River Basin

Drought has occurred in several tributary basins of the Mississippi River Watershed for the last 4 years. Dry conditions were especially acute in the Ohio and Upper Mississippi Basins during this spring and summer. The combination of dry conditions for the last 2 to 4 years in the Missouri Basin, and this year in the Upper Mississippi, Ohio, and recently in the Tennessee Basins, has resulted in record to near-record low flows in parts of the Mississippi River that caused barges to run aground. To make matters worse, the low flows upstream were compounded by a very hot and dry summer in the Lower Mississippi Basin, consequently leading to saltwater intrusion concerns in southern Louisiana.

The Upper Mississippi River Basin was extremely dry during May-August 2023. Precipitation during September and October improved drought conditions in the basin, but the earlier dryness was so acute that May-October 2023 still ranked as the 12th driest such period in the 1895-2023 record. April-October ranked as the 13th driest such 7-month period, and the last 12 months were the 37th driest November-October. According to the USDM, 43.6% of the basin was in moderate to extreme drought at the end of October, down from a peak of 89.9% which occurred on July 11.

The Ohio River Basin experienced extreme dryness during May-June 2023 and again in September, with a wet interlude in July-August. The September dryness resulted in the 24th driest September-October, with November-October ranking as the 40th driest such 12-month period. According to the USDM, 20.1% of the basin was in moderate to extreme drought at the end of October, down from a peak of 37.2% which occurred on October 17.

The Missouri River Basin experienced very dry conditions during 2020-2022, with wet conditions returning during 2023. Basinwide, 2022 had the 11th driest November-October, 2021 the 36th driest, and 2020 the 17th driest November-October. Taken together, the 36-month period November 2019-October 2022 ranked as the seventh driest such 36-month period in the 1895-2023 record. This prolonged dryness lowered groundwater levels which still haven't recovered in parts of the basin. Groundwater is an important source of water for streamflow. According to the USDM, 23.3% of the basin was in moderate to extreme drought at the end of October, down from a 2023 peak of 64.5% at the beginning of the year. At the height of the latest drought episode, 79.0% of the Missouri Basin was in drought on March 15, 2022.

Dry conditions in the Tennessee River Basin occurred only recently, with September-October 2023 ranking as the third driest such 2-month period on record. Abundant precipitation earlier in the year gave the basin the 65th driest (65th wettest) November-October 12-month period. According to the USDM, 94.3% of the Tennessee Basin was in moderate to extreme drought at the end of October, which is a rapid rise from less than 1% on September 19.

The Lower Mississippi River Basin has had dry conditions most of the months during this year, especially during the spring and summer, with July-August the period of most extreme dryness. May-October 2023 ranked as the eighth driest such 6-month period on record, with the last 12 months being the 59th driest November-October. According to the USDM, 80.6% of the Lower Mississippi Basin was in moderate to exceptional drought at the end of October, which is a rapid rise from less than 10% on June 13.

Rio Grande River Basin

The Rio Grande River Basin has been unusually dry and hot this year. The dry conditions were particularly widespread and acute from June to October, especially June and July. Most months were abnormally warm, especially starting in May. The basin had the warmest May-October and eighth driest June-October in the 1895-2023 record. In fact, every multi-month period from April-October through September-October, plus February-October and December-October, was warmest on record. May-October was the 13th driest such 6-month period and the last 12 months ranked as the tenth driest November-October. The entire basin (100%) was in moderate to extreme drought, based on the Palmer Drought Index, at the end of October, which is more than last month. According to the USDM, 90.8% of the basin was in moderate to exceptional drought, which is a little less than last month. Both the PDSI and USDM show that the Rio Grande Basin has been in cyclical drought for the last 23 years. The Palmer Drought Index reveals that the basin has experienced frequent drought for the last 123 years, especially in the 1950s and since 2000.

Hawaii

Drier-than-normal conditions dominated the main Hawaiian Islands during October 2023 and the last 2 to 6 months. Oahu to Maui were mostly drier than normal, and the Big Island had a mixed precipitation anomaly pattern, at 7- to 9-month time scales. Oahu, Maui, and windward parts of the Big Island were drier than normal at 12 months. At longer time scales, drier-than-normal conditions dominated Oahu to Maui and windward parts of the Big Island (precipitation anomaly maps for the last 1, 2, 3, 4, 6, 7, 9, 10, 12, 24, 36, 48, 60 months) (climate engine model percent of normal precipitation map for the last month).

Hilo, Hawaii had the driest October in the 1949-2023 record. If years with too much missing data are excluded, Hilo also had the driest June-October.

Monthly streamflow was below normal across most of the main islands. Based on satellite analyses (stressed vegetation, drought stress, VHI), vegetation was stressed across the main islands.

Moderate to extreme drought expanded across Hawaii during October, with the drought area growing to cover about 93.3% of the state on the October 31, 2023 USDM map. The peak value of 94.8% on October 24 exceeded the previous record of 94.0% in the 2000-2023 USDM period of record that last occurred on September 6, 2022.

Alaska

October 2023 was drier than normal in southwestern Alaska and southern parts of the panhandle, with some dryness at eastern interior stations. Dryness in the southwest persisted at the 2- to 3-month time scales. The last 4 to 12 months were drier than normal at scattered stations from the south coastal to interior regions and in the Aleutians and southern panhandle, but wetter-than-normal conditions otherwise dominated. Dryness in the south central and Aleutian regions was evident at longer time scales (low elevation station precipitation anomaly maps for the last 1, 2, 3, 4, 6, 7, 9, 10, 12, 24, 36, 48, 60 months) (high elevation SNOTEL station precipitation percentile maps for the last 1, 6, and 12 months) (SNOTEL basin and station percent of normal precipitation maps for the last 1, 6, and 12 months) (climate division precipitation rank maps for the last 1, 3, 6, 10, and 12 months) (climate engine model percent of normal precipitation map for the last month) (Leaky Bucket model precipitation percentile map).

October temperatures were warmer than normal in the Aleutians, panhandle, Gulf of Alaska Coast, and North Slope, while near- to below-normal temperatures dominated in the interior, eastern, and western areas. This pattern persisted at the 2-month time scale, but warmer-than-normal temperatures began to dominate at 3 months. Warmer-than-average temperatures dominated at longer time scales, when compared to the long-term (1926-2022) average. But when compared to more recent (1991-2020) normals, near to cooler-than-normal temperatures were evident at some western to central stations because of a pronounced warming trend in recent decades (low elevation station temperature anomaly maps for the last 1, 2, 3, 10, 12 months) (climate division temperature rank maps for the last 1, 3, 6, 10, and 12 months) (gridded temperature percentile maps for the last 1, 3, and 10 months) (Leaky Bucket model temperature percentile map).

Monthly streamflow was mostly near to above normal, except in the Cook Inlet, Northwest Gulf, Bristol Bay, and South Panhandle areas where it was mostly below normal. Satellite observations of vegetative health (stressed vegetation, drought stress, VHI) revealed areas of drought-related stress. Satellite-based observations of groundwater and soil moisture (GRACE root zone and GRACE surface soil moisture, Leaky Bucket modeled soil moisture) suggested some dryness was occurring in the southeast.

One remaining spot of abnormal dryness persisted at about 1.1% of the state on the October 31, 2023 USDM map.

Puerto Rico and U.S. Virgin Islands

October 2023 was drier than normal in western to central parts of Puerto Rico (PR), but the month was wetter than normal across the U.S. Virgin Islands (USVI) and the rest of PR. Drier-than-normal conditions dominated in the USVI and the western half of PR for the last 2 months. The USVI were drier than normal at longer time scales. Drier-than-normal conditions dominated PR at the 3- to 6-month time scales except along the southern and eastern coast. PR stations in the west, north, and east were dry at 7 to 12 months, with a mixed precipitation anomaly pattern dominated at longer time scales (radar-based precipitation anomaly estimates for the last 1, 2, 3, 6, 10, and 12 months) (low elevation station precipitation anomaly maps for the last 1, 2, 3, 4, 6, 7, 9, 10, 12, 24, 36, 48, 60 months) (climate engine model percent of normal precipitation map for the last month: PR and USVI, Caribbean and Gulf of Mexico region).

Temperatures were consistently warmer than normal for the last 12 months, with record to near-record warmth during the summer to early fall (low elevation station temperature anomaly maps for the last 1, 2, 3, 10, 12 months). San Juan, PR had the warmest October, September-October, August-October, July-October, June-October, and May-October in the 1899-2023 record. Rohlsen Airport on St. Croix had the warmest October, September-October, August-October, and June-October in the 1951-2023 record. The excessive heat increased evapotranspiration which made the dry conditions worse.

Root zone analyses indicated that soil conditions were moist across much of PR, but dry along the southwestern coast and a few areas in the north and eastern interior (root zone soil saturation fraction). Satellite observations of vegetative health (stressed vegetation for PR and USVI, drought stress for PR and USVI, VHI for PR and USVI) revealed areas of drought-related stress. Monthly streamflow on PR showed below-normal streams in northwestern areas. In the USVI, beneficial rains raised the groundwater level near the end of October at St. John and St. Thomas. There was some improvement of the groundwater level at St. Croix early in the month, but levels resumed their downward trend later in the month. For the most part, groundwater levels have been declining since the beginning of the year. The end-of-October groundwater level was well into the bottom third of the historical record at St. Croix, but had improved to the mid to upper levels at St. Thomas and St. John.

In the USVI, exceptional drought improved to severe drought (D2) on St. Croix and St. Thomas, while drought and abnormally dry conditions ended on St. John. Moderate drought shrank to cover about 2.6% of PR on the October 31, 2023 USDM map.

CONUS State Precipitation Ranks

October 2023 was drier than normal across much of the West, from the Lower Mississippi Valley to East and Gulf of Mexico Coasts, and across parts of the central and northern Plains and Ohio Valley. Fourteen states had a precipitation rank in the driest third of the 129-year historical record for October, including one that ranked in the top ten driest category — North Carolina (tenth driest) — and three that were close: Tennessee (12th driest) and Mississippi and Virginia (both 13th driest).

August-October 2023 was drier than normal from the Southwest to central and southern Plains, from the Lower Mississippi Valley to East Coast, in parts of the Midwest, and in a few other areas scattered across the country, with record dry conditions in the Lower Mississippi Valley. Twelve states had a precipitation rank in the driest third of the 1895-2023 historical record, including two that ranked in the top ten driest category — Mississippi (second driest) and Louisiana (third driest).

May-October 2023 was drier than normal along the West Coast, in the Southwest, along the Gulf of Mexico Coast, from the central Plains to Mississippi Valley, and from the Ohio and Tennessee Valleys to the Mid-Atlantic coast. Nineteen states had a precipitation rank in the driest third of the 1895-2023 historical record, including three that ranked in the top ten driest category — Louisiana (second driest), Arizona (eighth driest), and Minnesota (tenth driest) — and three that were close: Mississippi and Iowa (both 11th driest), and Wisconsin (12th driest).

The year to date (January-October 2023) was drier than normal across most of the Pacific Northwest, the Southwest to Gulf of Mexico Coast, the central Plains to Mid- and Upper Mississippi Valley, and from the Ohio Valley to Mid-Atlantic Coast, with record dryness occurring in the Lower Mississippi Valley. Sixteen states had a precipitation rank in the driest third of the historical record, including two that ranked in the top ten driest category — Maryland (seventh driest) and Washington (tenth driest) — and one that was close: Louisiana (11th driest).

The last 12 months (November 2022-October 2023) were drier than normal across parts of the Pacific Northwest, much of the Southwest to Gulf of Mexico Coast, the central Plains to Mid- and Upper Mississippi Valley, and from the Ohio Valley to Mid-Atlantic Coast. Ten states had a precipitation rank in the driest third of the historical record. None ranked in the top ten driest category, but one was close: New Mexico (14th driest).

Agricultural Belts

During October 2023, the Primary Hard Red Winter Wheat agricultural belt generally was warmer and drier than normal, with wetter-than-normal conditions in the east and south. The month ranked as the 50th wettest and 36th warmest October, regionwide, in the 1895-2023 record.

According to the U.S. Department of Agriculture (USDA), as of October 31, 2023, drought affected approximately 23% of barley production, 36% of corn production, 49% of cotton production, 49% of sorghum production, 38% of soybean production, 36% of spring wheat production, 42% of winter wheat production, 36% of hay acreage, 37% of the cattle inventory, 23% of the milk cow inventory, and 32% of the sheep inventory. Based on October 29 USDA statistics, 18% of the nation's winter wheat crop and 37% of the nation's pasture and rangeland were in poor to very poor condition, and 39% of the nation's topsoil and 50% of the subsoil were short or very short of moisture (dry or very dry). The table below lists the end-of-October soil moisture, pasture and rangeland, and winter wheat condition by state, with those states having 30 percent or more of topsoil or subsoil moisture short or very short, or 30 percent or more of the crop or pasture and rangeland in poor or very poor condition, highlighted in yellow:

Statewide topsoil moisture, subsoil moisture, and crop condition table

U.S.-Affiliated Pacific Islands

The NOAA National Weather Service (NWS) offices, the Pacific ENSO Applications Climate Center (PEAC), and partners provided reports on conditions across the Pacific Islands.

In the U.S. Affiliated Pacific Islands (USAPI) (maps — Federated States of Micronesia [FSM], Northern Mariana Islands, Marshall Islands [RMI], Republic of Palau [ROP], American Samoa, basinwide), October 2023 was drier than normal in American Samoa and parts of the Marshall Islands, Marianas, and FSM, but near to wetter than normal in most other areas.

Monthly precipitation amounts were below the monthly minimum needed to meet most water needs (4 inches in the Marianas and Pago Pago, and 8 inches elsewhere) at Jaluit in the Marshalls. October precipitation was above the monthly minimums at the rest of the stations across the USAPI. The 4- and 8-inch thresholds are important because, if monthly precipitation falls below the threshold, then water shortages or drought become a concern.

The tropical Pacific climatology can experience extremes in precipitation, from very low precipitation during the dry season to very high precipitation during the wet season. This can result in monthly normal precipitation values that are different from the monthly minimum needed to meet most water needs, and this can lead to percent of normal values that seem odd. This was the case during October 2023, which is in the wet season for northern stations in Micronesia, and in the dry season for American Samoa, Kosrae, and Kapingamarangi.

Precipitation was above the monthly minimum but below normal (1981-2010 normal), because the normals are high, at:

  • Kosrae: October 2023 precipitation 9.44 inches, October normal mean 11.52 inches, October normal median 10.94 inches.
  • Majuro: October 2023 precipitation 10.98 inches, October normal mean 13.27 inches, October normal median 12.73 inches.
  • Pago Pago: October 2023 precipitation 8.45 inches, October normal mean 10.11 inches, October normal median 9.26 inches.
  • Pohnpei: October 2023 precipitation 12.71 inches, October normal mean 15.27 inches, October normal median 15.27 inches.
  • Saipan: October 2023 precipitation 9.80 inches, October normal mean 11.32 inches, October normal median 10.62 inches.
  • Yap: October 2023 precipitation 10.74 inches, October normal mean 12.25 inches, October normal median 12.18 inches.
  • Nukuoro: October 2023 precipitation 8.48 inches, October normal mean 10.31 inches.
  • Pingelap: October 2023 precipitation 12.08 inches, October normal mean 12.39 inches.
  • Wotje: October 2023 precipitation 8.24 inches, October normal mean 8.70 inches.

In the table below, the station identified as Koror is Palau International Airport (Airai).

Pacific Island Percent of 1981-2010 Normal Median Precipitation
Station Name Nov
2022
Dec
2022
Jan
2023
Feb
2023
Mar
2023
Apr
2023
May
2023
Jun
2023
Jul
2023
Aug
2023
Sep
2023
Oct
2023
Nov-
Oct
Chuuk93%116%92%215%85%137%191%118%130%118%112%110%120%
Guam NAS77%182%350%188%263%198%916%146%86%132%98%152%145%
Kapingamarangi55%53%166%47%116%141%137%145%162%121%256%117%114%
Koror88%105%187%102%185%77%165%77%145%125%130%108%114%
Kosrae107%99%131%188%67%120%87%166%132%104%123%153%102%
Kwajalein81%88%224%50%189%188%345%143%45%81%61%103%112%
Lukonor94%54%124%68%96%77%61%116%75%74%115%136%78%
Majuro91%90%157%138%169%151%102%105%70%95%56%86%102%
Pago Pago118%71%114%110%106%152%168%109%102%42%156%91%98%
Pohnpei85%74%136%146%109%141%145%121%148%219%156%83%126%
Saipan60%130%441%118%138%192%225%92%46%142%109%92%117%
Yap68%131%133%118%137%104%131%121%168%145%70%88%113%
Pacific Island Precipitation (Inches)
Station Name Nov
2022
Dec
2022
Jan
2023
Feb
2023
Mar
2023
Apr
2023
May
2023
Jun
2023
Jul
2023
Aug
2023
Sep
2023
Oct
2023
Nov-
Oct
Chuuk9.83"13.00"9.34"15.60"7.09"17.14"21.57"13.73"15.56"15.23"13.07"12.70"163.86"
Guam NAS5.66"9.32"14.02"5.69"5.45"5.01"31.15"9.00"8.69"19.47"12.46"17.40"143.32"
Kapingamarangi5.11"5.23"15.23"4.37"13.24"19.19"16.59"20.04"22.86"9.87"25.45"9.55"166.73"
Koror10.00"11.76"19.04"8.74"13.74"5.60"19.53"13.44"26.81"16.86"15.26"12.80"173.58"
Kosrae14.74"15.95"21.87"24.25"10.81"21.08"15.41"24.30"19.67"14.72"17.52"16.79"217.11"
Kwajalein9.09"5.88"7.08"1.32"4.43"9.87"23.18"9.93"4.45"7.86"6.60"11.46"101.15"
Lukonor8.52"6.06"10.45"6.08"8.92"8.68"7.13"13.55"11.89"10.33"11.63"15.43"118.67"
Majuro12.21"10.30"12.14"9.51"11.12"14.23"10.35"11.56"7.87"11.07"6.27"10.98"127.61"
Pago Pago11.93"9.10"15.19"13.19"11.34"14.25"16.19"5.81"5.64"2.26"10.18"8.45"123.53"
Pohnpei12.66"11.86"17.94"13.99"14.29"25.90"29.02"17.94"22.76"31.21"19.57"12.71"229.85"
Saipan3.39"5.01"11.16"3.05"2.61"5.05"5.35"3.34"4.13"18.62"11.03"9.80"82.54"
Yap5.99"11.17"8.51"6.11"6.26"5.86"10.28"14.59"25.35"21.43"9.46"10.74"135.75"
Pacific Island 1981-2010 Normal Median Precipitation (Inches)
Station Name Nov
2022
Dec
2022
Jan
2023
Feb
2023
Mar
2023
Apr
2023
May
2023
Jun
2023
Jul
2023
Aug
2023
Sep
2023
Oct
2023
Nov-
Oct
Chuuk10.61"11.25"10.10"7.25"8.32"12.47"11.30"11.66"11.98"12.86"11.71"11.51"136.77"
Guam NAS7.38"5.11"4.01"3.03"2.07"2.53"3.40"6.18"10.14"14.74"12.66"11.44"99.09"
Kapingamarangi9.27"9.84"9.15"9.27"11.43"13.64"12.08"13.78"14.15"8.13"9.93"8.19"145.85"
Koror11.39"11.16"10.18"8.56"7.44"7.32"11.83"17.48"18.53"13.50"11.77"11.84"152.90"
Kosrae13.83"16.11"16.67"12.93"16.06"17.51"17.75"14.64"14.91"14.22"14.22"10.94"213.87"
Kwajalein11.28"6.66"3.16"2.64"2.35"5.26"6.72"6.93"9.87"9.74"10.74"11.18"90.41"
Lukonor9.08"11.27"8.41"8.93"9.26"11.31"11.69"11.65"15.93"14.04"10.15"11.32"151.36"
Majuro13.44"11.39"7.74"6.88"6.58"9.42"10.11"11.01"11.17"11.69"11.17"12.73"125.25"
Pago Pago10.14"12.84"13.34"12.00"10.68"9.39"9.66"5.33"5.55"5.38"6.53"9.26"125.57"
Pohnpei14.83"16.08"13.18"9.55"13.17"18.41"19.96"14.81"15.43"14.26"12.55"15.27"182.36"
Saipan5.61"3.85"2.53"2.59"1.89"2.63"2.38"3.62"8.91"13.13"10.09"10.62"70.25"
Yap8.83"8.51"6.39"5.19"4.56"5.63"7.85"12.04"15.08"14.82"13.50"12.18"120.31"

As measured by percent of normal precipitation, no station was drier than normal at all time scales in the short term (October and the last 3 months [August-October]) and long term (year to date [January-October] and last 12 months [November 2022-October 2023]). However, Pago Pago was drier than normal for 3 of the time periods and wetter than normal for the year to date. Majuro and Yap were drier than normal in the short term and near to wetter than normal in the long term. Lukunor was drier than normal in the long term and near to wetter than normal in the short term. Kosrae was drier than normal for October and the last 12 months but near to wetter than normal for the other 2 time periods. Pohnpei and Saipan were drier than normal for October but wetter than normal for the other 3 time periods. Kwajalein was drier than normal at the 3-month time scale but near to wetter than normal at the other 3 time scales. Airai, Chuuk, Guam, and Kapingamarangi were wetter than normal for all 4 time periods.

Based on percent of normal average (instead of normal median values), in the Marianas Islands, October and the last 4 to 6 months were drier than normal across the main islands except Guam. Wetter-than-normal conditions dominated at the other time scales up through the last 24 months, except for Saipan at the 2-month time scale. A mixed precipitation anomaly pattern was evident at longer time periods (percent of normal precipitation maps for the last 1, 2, 3, 4, 6, 7, 9, 10, 12, 24, 36, 48, 60 months).

Based on percent of normal average (instead of normal median values), in the Marshall Islands, the last 1 to 4 months were drier than normal across most of the islands. The last 6 to 10 months were drier than normal in the southwest and northeast but wetter than normal at the other primary stations. Wetter-than-normal conditions dominated at the 12- to 48-month time scales. Longer time periods were drier than normal in the southwest (Jaluit) and north (percent of normal precipitation maps for the last 1, 2, 3, 4, 6, 7, 9, 10, 12, 24, 36, 48, 60 months).

According to the October 31 USDM produced for the USAPI, Kwajalein and Wotje (RMI) were abnormally dry, while the rest of the USAPI stations were free of drought and abnormal dryness. Satellite observations of vegetative health (drought stress, stressed vegetation, VHI) indicated there were some areas of stressed vegetation on Guam, but little concern for drought.

October 2023 precipitation ranks were mostly in the mid-range between wet and dry, based on data available at the time of this report. Lukunor and Jaluit had long-term dryness that ranked in the top ten driest category, while Lukunor, Ailinglaplap, and Mili had October precipitation that ranked in the top ten wettest category:

  • Lukunor: sixth driest November-October (in a 27-year record for the 12-month time scale) but third wettest October (in 39 years of data for October).
  • Jaluit: 14th driest October (40 years) but fourth driest May-October, fifth driest June-October and April-October through February-October, and seventh driest November-October.

At the wet end of the scale:

  • Ailinglaplap had the sixth wettest October (40 years).
  • Mili had the seventh wettest October (40 years) and wettest June-October, May-October, and January-October through November-October.

The following analysis of historical data for the USAPI stations in the Global Historical Climatology Network-Daily (GHCN-D) dataset, augmented with fill-in data from the 1981-2010 Normals, helps put the current data into historical perspective by computing ranks based on the period of record. The table below lists the precipitation ranks for October 2023, May-October 2023 (last 6 months), and November 2022-October 2023 (the last 12 months). Some stations have a long period of record and their dataset is fairly complete, while other stations have a shorter period of record and the dataset has some missing data.

October 2023 USAPI Precipitation Ranks (1 = driest)
StationOctober 2023May-Oct 2023Nov 2022-Oct 2023Period of Record
RankYearsRankYearsRankYears
Ailinglaplap3540233929371981-2023
Airai3973667162711951-2023
Chuuk3973627262721951-2023
Fananu8944--22003-2023
Guam5567676765661957-2023
Jaluit14404397371981-2023
Kapingamarangi2434232320221962-2023
Kosrae1355294421371954-2023
Kwajalein3472457241711952-2023
Lukunor37399276271981-2023
Majuro217096931691954-2023
Mili3440383835351981-2023
Nukuoro1241303934381981-2023
Pago Pago2358325827571966-2023
Pingelap2640938--341981-2023
Pohnpei2273717269721951-2023
Saipan1643304330341981-2023
Ulithi2840373831341981-2023
Utirik--18--6--21985-2020
Woleai2539--29--281968-2023
Wotje2340153928361981-2023
Yap2873637253721951-2023
Map of USAPIOctober 2023 Precipitation (Inches)
Map of USAPI October 2023 Percent of Normal Precipitation
Map of USAPI August 2023-October 2023 Percent of Normal Precipitation
Map of USAPI January-October 2023 Percent of Normal Precipitation
Map of USAPI November 2022-October 2023 Percent of Normal Precipitation

SPI values for seven time periods for Pacific Islands, computed by the Honolulu NWS office.

SPI values for seven time periods for Pacific Islands

NOAA Regional Climate Centers

More information, provided by the NOAA Regional Climate Centers and others, can be found below.

Southeast

As noted by the Southeast Regional Climate Center, monthly precipitation was below average across much of the Southeast in October and mean temperatures varied across the region. The driest locations were found across northern portions of Alabama and Georgia, western and eastern portions of North Carolina, and northern Virginia, where many locations recorded less than an inch and, in some cases, less than half an inch of precipitation for the month (less than 25 percent of normal). Several locations ended long streaks of consecutive dry days during the month. On the 6th, Charlotte, NC, Athens, GA, and Atlanta, GA ended streaks of 18 consecutive days without measurable precipitation, while Montgomery, AL and Greenville-Spartanburg, SC ended streaks of 24 consecutive days on the 10th and 11th, respectively. In contrast, precipitation was above average across central portions of Georgia and South Carolina, and isolated portions of Florida.

In the Caribbean, precipitation was below average across the western part of Puerto Rico (as little as 50 percent of normal) and above average across the eastern part of the island, including San Juan, which recorded 9.73 inches (247 mm) for the month. Of this, 5.20 inches (132 mm) fell on the 27th, making it the wettest October day on record (since 1898). Precipitation was also above average across the U.S. Virgin Islands. Several stations recorded 5 to 10 inches (127 to 254 mm) of precipitation, including Cyril King Airport on Saint Thomas, which recorded 8.69 inches (221 mm) for the month. Much of this precipitation came from tropical systems. Tropical Storm Philippe dropped 2 to 4 inches (51 to 102 mm) of precipitation across Saint Thomas and Saint Croix between the 3rd and 5th of the month. A few gauges on Saint John, including Cruz Bay and Trunk Bay, recorded over 8 inches (203 mm) from this event. Philippe also dropped over 5 inches (127 mm) of precipitation across eastern portions of Puerto Rico. A trough of low pressure combined with rain bands from Hurricane Tammy dropped another 2 to 4 inches (51 to 102 mm) of precipitation across Puerto Rico and up to an inch across the Virgin Islands from the 18th through the 23rd of the month.

Drought conditions continued to worsen across the Southeast in October. Extreme (D3) drought emerged across northern portions of Alabama and Georgia and expanded across southern Georgia and the western Panhandle of Florida. Severe (D2) drought expanded across northern Virginia and southern Georgia, and emerged across central Alabama, northern portions of Georgia and South Carolina, and western portions of North Carolina. Moderate (D1) drought also expanded in these areas, as well as across central and southern portions of North Carolina and Virginia, where abnormal dryness (D0) expanded to the east. A small area of extreme (D3) to moderate (D1) drought persisted along the West Coast of Florida, while the rest of the Peninsula remained drought-free. Small areas of abnormal dryness (D0) were eliminated across central Georgia and the eastern Panhandle of Florida due to heavy precipitation in the middle of the month. Overall, about 70 percent of the region was abnormally dry or in drought by the end of October. In the Caribbean, drought conditions improved in October. Moderate (D1) drought was eliminated across eastern Puerto Rico and contracted across the northwest part of the island. Drought was eliminated on Saint John, while conditions on Saint Thomas and Saint Croix improved from exceptional (D4) drought at the beginning of the month to severe (D2) drought at the end of the month.

The cool and dry weather pattern in October continued to negatively affect agriculture in the Southeast. The dry ground made it difficult to harvest peanuts and plant winter grains and forage, while cooler temperatures slowed the maturity of several crops. Cotton and peanut yields are expected to be below average across parts of southern Georgia and the Florida Panhandle. The unseasonably warm and dry conditions over the summer and early fall led to reduced quantity and size of pumpkins and apples. The lack of precipitation led to more insects and increased disease pressures, including citrus greening in Florida. Hay supplies were also negatively affected by the dry weather. Many farmers were only able to complete up to two cuttings due to the lack of regrowth, which was also stunted due to cooler temperatures over the past several weeks. Cattle were being fed supplemental hay and calves were being sold early due to water shortages. On the other hand, the dry weather helped some farmers wrap up the harvest of corn and make strong progress on the harvest of early-planted cotton and soybeans. In Puerto Rico, recent precipitation delayed some planting, but was largely beneficial for many crops, particularly pastures. Some pond recharge was noted across the U.S. Virgin Islands and field conditions were improving on Saint John. However, the precipitation on Saint Croix was not able to penetrate the soil. Hay shortages persisted and significant losses to livestock and poultry continued to be reported.

South

As explained by the Southern Regional Climate Center, temperatures across the Southern region during October were typically one to four degrees F above normal. Wet conditions in the west led to flooding and damage to homes, while very dry conditions in the east led to deterioration of drought conditions. October precipitation was well above normal across much of Texas, Oklahoma, and Arkansas, except for portions of the Texas and Oklahoma Panhandles and far west Texas; well below-normal precipitation was observed across Louisiana, Mississippi, and Tennessee.

During October, the Southern region saw improvement in drought conditions across the western portions of the region, particularly the reduction of extreme or exceptional drought from central Texas north through southern Oklahoma. Drought conditions in the eastern portions of the region worsened, including the emergence of extreme drought in Tennessee and northern Mississippi, and exceptional drought in northern Mississippi. Extreme or exceptional drought, according to the USDM, did see reductions in total area being affected within the region, with extreme drought decreasing from 19 percent on October 3rd to 12 percent on October 31st and exceptional drought decreasing from 14 percent to ten percent over the same time period. The USDA Crop Progress Report for October 29th reported that the cotton crops in Texas and Oklahoma were only reporting ten and three percent, respectively, of crops to be in Good to Excellent condition, while Louisiana, Mississippi, Arkansas, and Tennessee fared much better with 48 percent, 45 percent, 74 percent, and 83 percent being rated as Good to Excellent respectively. Increased flows on the Mississippi River during October appear to have prevented a saltwater wedge traveling up the Mississippi River from the Gulf of Mexico from reaching New Orleans, Louisiana, but communities downstream have had their water systems badly affected by the saltwater intrusion.

Midwest

As described by the Midwest Regional Climate Center, the average October temperature for the Midwest was 53.7 degrees F (12 degrees C), which was 2.3 degrees F (1.3 degrees C) above the 1991-2020 normal, and October precipitation totaled 3.49 inches (89 mm) for the region, which was 0.39 inch (10 mm) above normal, or 113 percent of normal. Moisture was quite variable across the region. Precipitation totaled 125-300 percent of normal along an axis stretching from the Iowa-Minnesota border eastward to northwest Ohio. Conversely, totals were 25-75 percent of normal for much of the lower Midwest. Preliminary statewide precipitation totals ranged from 0.84 inch (21 mm) below normal in Kentucky to 1.35 inches (34 mm) above normal in Wisconsin.

Increased moisture helped reduce the severity and extent of dryness and drought throughout the Midwest in October. The month concluded with about 65 percent of the region affected by dryness or drought; a 21 percent improvement compared to the beginning of October. Portions of Minnesota, Wisconsin, and Indiana had 2-3 class improvements on the USDM map over the month. Drought was the most severe in eastern Iowa and west-central Missouri. Drought remained widespread along and west of the Mississippi River and sporadic to the east. About 42 percent of the region had no dryness or drought by month's end.

Northeast

As summarized by the Northeast Regional Climate Center, October was a warm and dry month for the region. The Northeast had its seventh warmest October since records began in 1895 with an average temperature of 54.1 degrees F, 3.9 degrees F above normal. The Northeast saw 3.50 inches of precipitation during October, which was 83 percent of normal. October precipitation for the 12 Northeast states ranged from 36 percent of normal in Delaware to 108 percent of normal in Vermont, with ten states being drier than normal. This October ranked as Delaware's 15th driest on record and Maryland's 18th driest.

The USDM from October 3 showed less than 1 percent of the Northeast in severe drought, two percent in moderate drought, and 15 percent as abnormally dry. Beneficial precipitation in western portions of New York, Pennsylvania, and West Virginia chipped away at drought and abnormal dryness. However, areas such as central New York, eastern Pennsylvania, western New Jersey, northern Delaware, and southern and eastern Maryland experienced a dry October, with increasing precipitation deficits driving an expansion of abnormal dryness. Improving conditions in some areas counterbalanced deteriorating conditions in other areas, with the USDM from October 31 also showing less than 1 percent of the Northeast in severe drought, two percent in moderate drought, and 15 percent as abnormally dry. At times during October, USGS 7-day average streamflow and/or groundwater levels were below normal or lower in western and central New York and an area from eastern West Virginia through Maryland and southern Pennsylvania into southern New Jersey, with a couple of gauges reporting record low flows or levels. Daily drought monitoring was reinstated along the Potomac River upstream from Washington, D.C. In Pennsylvania, more than a dozen water suppliers asked customers to voluntarily conserve water and a few implemented mandatory restrictions. For instance, Lock Haven declared a drought emergency and had mandatory water restrictions in place.

High Plains

As discussed by the High Plains Regional Climate Center, this October wrapped all seasons into a month in the High Plains. Scorching summerlike warmth and severe weather began the month, while the month ended with subzero temperatures and snow. The overall trend of warmer temperatures continued into yet another month. October brought precipitation to much of the northern part of the region, while the southern portions received isolated but plentiful amounts.

Improvements to drought conditions were the major story this month. The heavy bouts of rain led to large-scale improvements in several states. Overall, abnormally dry to exceptional drought (D0-D4) was reduced by over 5 percent in the High Plains. Nebraska experienced the most significant changes, with up to 3 classes of improvement. Moderate to exceptional drought (D1-D4) was over 20 percent, with conditions nearly erased from the northern part of the state. Kansas also greatly benefited, with extreme drought (D3) reduced by 13 percent and D4 completely eliminated for the first time in well over a year. Parts of the Dakotas observed up to 2 classes of improvement in response to above-normal precipitation.

West

As summarized by the Western Regional Climate Center, the western United States generally saw below-normal precipitation and above-normal temperatures in October. One exception was central and eastern Montana where cool and wet conditions persisted for the month with an anomalous early season snowfall event for some locations near the end of the month. Dry and warm conditions drove expanded drought across parts of the Southwest; some drought improvements occurred in the Pacific Northwest due to the onset of a more consistent stormy and wet pattern.

Precipitation was well below normal (less than 50 percent) across most of California, Arizona, western New Mexico, southern Utah, the Washington Cascades, and the Idaho Panhandle. Central and eastern Montana saw above-normal precipitation and snowfall. Most of southern California saw no measurable precipitation in October (this has occurred numerous times in the past) with departures roughly 0.25-0.5 inch below normal. The Cascade Range in northern Washington was particularly dry with many of the mountain SNOTEL stations measuring 30-40 percent of normal precipitation for the month and departures more than five inches below normal. Much of central and eastern Montana saw a top ten wettest October on record and well above normal snowfall due to the cold temperatures.

According to the USDM at the end of October, 31 percent of the West was in drought. Areas of extreme (D3) and exceptional (D4) drought are found in Arizona, New Mexico, Oregon, Washington, and Montana. One-class drought degradations occurred in parts of Arizona, New Mexico, and Utah with drought improvements in Oregon, Washington, and Montana.

Alaska summary: It was a warm month for the Panhandle, Aleutian Peninsula, and North Slope with temperatures 1-4 degrees Fahrenheit above normal. Across central Alaska temperatures were slightly below normal (1-2 degrees Fahrenheit). Precipitation anomalies were mixed across the state but southwest Alaska, including the Kenai Peninsula and Aleutian Peninsula, was dry with anomalies generally 2-5 inches below normal. Kenai saw its driest October on record with just 0.5 inch of precipitation (20 percent of normal) and Cold Bay had its sixth driest with 2.25 inches of precipitation (46 percent of normal).

Hawaii summary: October was an extremely dry month for all of Hawaii with most of the long-term climate stations receiving 70 percent of normal precipitation or less. The largest relative departures were found on the Big Island and Oahu where most stations received less than 25 percent of normal precipitation. Hilo saw its driest October on record with 1.36 inches of precipitation (13 percent of normal) which shattered the previous record low of 2.40 inches set in 1962. Dryness in October led to a few more areas of drought expansion on the USDM. At the end of October, 100 percent of Hawaii was at least abnormally dry (D0) and 93 percent of the state was at least in moderate drought (D1). Water restrictions and increased fire danger have resulted from the increased drought conditions. Upcountry, part of Maui County, has recently moved to a stage 2 water shortage due to worsening drought conditions. Daily water demand is exceeding supply by 20 percent and restrictions have been put in place to reduce use. The restrictions include irrigation, watering lawns, washing vehicles, and other nonessential activities. Shortage restrictions will remain in place until conditions change.

Additional Resources


Citing This Report

NOAA National Centers for Environmental Information, Monthly Drought Report for October 2023, published online November 2023, retrieved on April 13, 2024 from https://www.ncei.noaa.gov/access/monitoring/monthly-report/drought/202310.