Issued 11 August 2023

July 2023 Palmer Z-Index
U.S. Percent Area Wet or Dry January 1996 - July 2023
July 2023 /monitoring-content/sotc/drought/2023/07/mn-p-reg021dv00elem01-05072023.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 July 2023 consisted of a strong ridge of high pressure, which was anchored over the southern CONUS, and migrating shortwave troughs and closed lows that moved through the jet-stream flow across southern Canada. The ridge frequently extended northward across western Canada and Alaska, and it was part of a sub-tropical ridge system that extended eastward across the Caribbean and North Atlantic and westward across the North Pacific. The ridge oscillated between the Southwest and southern Plains as the month progressed, with its northern extension moving from western North America to the Great Plains and southern Canadian Prairies. Warmer- and drier-than-normal weather accompanied the ridge, with excessively hot temperatures plaguing the Southwest throughout the month. Several large wildfires burned across the western CONUS, with hundreds continuing to burn across Canada. The migrating Pacific weather systems weakened as they penetrated the western ridge, but were re-energized as they moved into an upper-level trough over eastern North America. Cold fronts and surface low pressure systems, that were associated with the weather systems, moved across the eastern half of the CONUS, bringing cooler-than-normal air to the northern and central Plains and Upper Midwest. They also generated areas of above-normal precipitation across parts of the Plains, Tennessee and Ohio Valleys, and eastern Great Lakes to Northeast.

The above-normal precipitation resulted in contraction or reduction of the intensity of drought over parts of the Great Plains, Mid-Mississippi Valley, Tennessee and Ohio Valleys, and eastern Great Lakes to Northeast. Some contraction of drought or abnormal dryness occurred in parts of Puerto Rico, Hawaii, and Alaska. Drought or abnormal dryness intensified or expanded in the Pacific Northwest, across the northern Plains to Upper Mississippi Valley, in the Southwest and southern Plains, along the western Gulf of Mexico Coast, and over parts of Puerto Rico, Hawaii, and Alaska. The excessive record heat, especially in the Southwest, increased evapotranspiration which exacerbated conditions where precipitation was below normal. Drought expansion exceeded contraction with the USDM-based national moderate-to-exceptional drought footprint across the CONUS increasing from 27.0% at the end of June to 28.1% at the end of July (from 22.6% to 23.5% for the 50 states and Puerto Rico).

According to the Palmer Drought Index, which goes back to the beginning of the 20th century, about 22.3% of the CONUS was in moderate to extreme drought at the end of July, which is an increase compared to the end of June.

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Drought conditions at the end of July, as depicted on the August 1, 2023 USDM map, included the following core drought and abnormally dry areas:

July 2023 /monitoring-content/sotc/drought/2023/07/20230801_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.

July 2023 Palmer Z-Index
July 2023 PHDI

Used together, the Palmer Z Index and PHDI maps show that short-term drought occurred in the Pacific Northwest to Upper Mississippi Valley, Southwest to western Gulf of Mexico Coast, and parts of the Carolina Coast, expanding or intensifying long-term drought (PHDI maps for July compared to June). Short-term wet conditions occurred from the Wyoming Rockies to parts of the northern Plains and in New England, maintaining or expanding long-term wet conditions, and across Nebraska to Oklahoma, in the Ohio Valley, and southern parts of the Northeast, 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.

July 2023 SPI
June-July 2023 SPI
May-July 2023 SPI
February-July 2023 SPI

The SPI maps illustrate how moisture conditions have varied considerably through time and space over the last two years. Dryness is evident across most of the West at the 1-month time scale and persists at the 2- to 12-month time scales in the Pacific Northwest and 2- to 9-month time scales in parts of the Southwest. The Upper Mississippi Valley is dry at 1 to 12 months, with the dryness extending to the Middle Mississippi Valley and parts of the Lower Mississippi Valley at 2 to 24 months. Parts to much of Texas is dry at 1 to 9 months and 24 months. Parts of the Southeast are dry at the 1-month time scale with dryness persisting along parts of the North Carolina coast at all time scales. Parts of the central Appalachians have dry conditions at 2 to 12 months. The western Great Lakes and parts of the Ohio Valley are dry at 3 months. Much of the West is wet at 9-12 months; western parts of the Great Plains are wet at 2- to 9-month time scales with northern parts of the Plains wet at 24 months; and parts to most of the Northeast is wet at all time scales.

November 2022-July 2023 SPI
August 2022-July 2023 SPI
August 2021-July 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, July marks the middle of climatological summer, which is the season when evapotranspiration reaches its annual maximum. During July 2023, temperatures were warmer than normal for much of the West, South, and Northeast, with record warm temperatures occurring across the Southwest, along the Gulf of Mexico coast, and in northern New England. In the Southwest, the record warmth during July 2023 far exceeded the previous record-warm Julys in Arizona and New Mexico. Most of the West and southern Plains was drier than normal, with record dryness occurring locally in the Southwest. The combination of increased evapotranspiration due to the heat, and lack of precipitation, resulted in more severe SPEI values than SPI values in the West and southern Plains during July. The July SPI values were slightly more extreme than the SPEI values in the northern Plains and Upper Mississippi Valley due to the combination of low precipitation but cooler-than-normal temperatures there. The 2-month SPEI was more extreme than the SPI in the Southwest but only a little more extreme in the Pacific Northwest. For the last 3 months, the SPEI was more extreme than the SPI in both the Southwest and Northwest. In both of these cases, the Pacific Northwest and Southwest had warmer- and drier-than-normal conditions (2-month temperature and precipitation anomaly maps; 3-month temperature and precipitation anomaly maps). Temperatures in the West moderated at the 6- to 12-month time scales, so the SPEI and SPI patterns were of similar magnitude across most of the CONUS, except the Northwest at 12 months where SPEI was more extreme (SPEI maps for the last 1, 2, 3, 6, 12 months) (SPI maps for the last 1, 2, 3, 6, 12 months).

The SPEI was more extreme than the SPI for the following states:

  • July SPEI for Arizona vs. July SPI. The SPEI was record dry and far more extreme than the SPI, which was only second driest on record.
  • July SPEI for New Mexico vs. July SPI. Like Arizona, the July 1-month SPEI for New Mexico was record dry and far more extreme than the corresponding SPI, which was only second driest on record.
  • May-July SPEI for Washington vs. May-July SPI. The SPEI was third driest on record and more extreme than the SPI, which was fifth driest.

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 (24-month temperature ranks, precipitation ranks, SPEI, SPI) (36-month temperature ranks, precipitation ranks, SPEI, SPI). In the southern Plains (Texas), the temperature anomalies were hot enough to make the SPEI more extreme than the SPI at these time scales.

For the western U.S., the last 12 months have seen temperatures that were near the long-term average, but most of the last 10 to 20 years have been a period of unusually warm temperatures across the West. There have also been periods of extreme dryness westwide during this period (this year being an exception). The combination of excessive heat and dryness has resulted in more extreme SPEI values than SPI values 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). This is especially the case for California, which had the seventh most extreme 72-month SPEI but a corresponding SPI that was only a little on the dry side.

Regional Discussion

Western United States

For the West as a whole, the last 12 months have been generally near to wetter than the long-term average for precipitation, and near to cooler than normal for temperature. July 2023 marked a departure from these conditions, as it was the driest and third warmest July in the 1895-2023 record, regionwide.

The extreme precipitation and temperature ranks for the region in July were largely due to extremes in two climate sub-regions — the Northwest (Pacific Northwest) and Southwest. The Southwest had the warmest and third driest July on record, while the Pacific Northwest ranked ninth driest and 12 th warmest. These regions (the Pacific Northwest in particular) have had extremes that have lasted for 2 to 3 months. In the Pacific Northwest, May-July 2023 ranked as the third warmest and 15th driest such 3-month period, and April-July 2023 ranked as the 13th warmest such 4-month period. The regional ranks mask local extremes, since parts of the coast especially had the driest May-July on record. In the Southwest, April-July ranked as the 16th driest and 25th warmest such 4-month period. It's particularly notable that recent decades have been persistently near to record warm for these regions at these time scales.

The dry and hot conditions in the Pacific Northwest and Southwest resulted in drought expansion in the western U.S. As of the end of July, 15.0% of the West was affected by moderate to extreme drought, based on the PDSI. This is more than the end of June. Drought had virtually ended in the western U.S. (based on the Palmer Index) only 4 months ago, but the drought area has steadily increased since then.

Upper Mississippi River Basin

The last 3 months have been very dry across the Upper Mississippi River Valley. This basin had the fourth driest May-July on record. This has resulted in a rapid increase in drought. According to the Palmer Drought Index, 35.9% of the basin was in moderate to extreme drought at the end of July. Based on the USDM, 77.6% of the basin was in moderate to exceptional drought.

Rio Grande River Basin

At the other end of the country, the Rio Grande River Basin had the second driest June-July, 16th driest May-July, and 21st driest November-July on record. The Rio Grande Basin has been in cyclical drought for many years. The last several months have seen a rapid increase in drought area, with the Palmer Drought Index indicating 77.9% of the basin was in moderate to extreme drought at the end of July and the USDM saying 59.3% of the basin was in moderate to exceptional drought.

Great Plains

The Great Plains region has been unusually dry for much of the last 3 to 4 years. Beneficial precipitation has fallen in recent months, especially in western areas. This has improved regionwide precipitation ranks for the Great Plains, with July ranking 56th wettest, May-July 32nd wettest, January-July 54th wettest, and the last 12 months (August 2022-July 2023) 42nd driest. The drought area has been decreasing, but the Palmer Drought Index still indicates 30.1% of the region was in moderate to extreme drought at the end of July.

Hawaii

Drier-than-normal conditions dominated most of the stations across the main Hawaiian Islands during July 2023 and June-July. May-July had a mixed precipitation anomaly pattern, with drier-than-normal conditions dominating the windward side of the Big Island and most stations on Maui, Molokai, and Oahu. The last 4 to 7 months were mostly wetter than normal, except for the windward side of the Big Island and Maui. Wetter-than-normal conditions dominated at 9-12 months. At longer time scales, windward sides of the islands were drier than normal and leeward sides wetter than normal, with a mixed pattern evident at 60 months (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).

Monthly streamflow was below normal at a few stations on Maui to Oahu but near to above normal at most other sites. Based on satellite analyses (stressed vegetation, drought stress, VHI), there were areas of vegetative stress this month on Oahu, Molokai, Maui, and the Big Island.

Severe drought returned to Hawaii during July, with the moderate to severe drought area shrinking to cover about 6.5% of the state on the August 1, 2023 USDM map.

Alaska

July 2023 was drier-than-normal in Alaska from the Southeast Interior region to the Panhandle, with record dryness occurring along the Northeast Gulf region and at some eastern interior stations; it was near to wetter than normal to the north and west. This precipitation anomaly pattern also existed at the 2-month time scale, with some dryness in the eastern interior and southern panhandle at 3 months. The eastern interior was dry at 4-6 months with dryness appearing along the Northeast Gulf. A mostly wetter-than-normal pattern dominated at 7-12 months. At longer time scales, it was mostly wetter than normal except for some drier-than-normal stations in the Northwest Gulf and Cook Inlet area (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, 2, 4, 7, 10, and 12 months) (SNOTEL basin and station percent of normal precipitation maps for the last 1, 2, 4, 7, 10, and 12 months) (climate division precipitation rank maps for the last 1, 3, 6, 7, and 12 months) (climate engine model percent of normal precipitation map for the last month) (Leaky Bucket model precipitation percentile map).

July temperatures were warmer than normal across most of the state, with near-normal temperatures in parts of the Southwest. This temperature anomaly pattern held at the 2- to 3-month time scales. Colder-than-normal temperatures dominated at the 4-month time scale, with below-normal temperatures in the west and above-normal temperatures in the east, north, and southeast at 6 to 12 months when compared to more recent (1991-2020) normals. But when compared to the long-term (1926-2022) average, temperatures were near to above average at 6-7 months and mostly warmer than average at 12 months. This is due to a pronounced warming trend in recent decades (low elevation station temperature anomaly maps for the last 1, 2, 3, 4, 7, 10, 12 months) (climate division temperature rank maps for the last 1, 3, 6, 7, and 12 months) (gridded temperature percentile maps for the last 1, 3, and 7 months) (Leaky Bucket model temperature percentile map).

Monthly streamflow was mostly near to above normal, except in the panhandle 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, GRACE surface, SMOS soil moisture, Leaky Bucket modeled soil moisture) suggested some dryness was occurring in the south and east. Reports of drought impacts have been received from the Glennallen area in southeast Alaska and include berries not producing as quickly, other vegetation dying, and low streamflow affecting fish wheels.

Areas of abnormal dryness and moderate drought expanded during July in the south and east. About 0.3% of the state was in drought, and abnormal dryness and drought covered 7.5% of the state, on the August 1, 2023 USDM map.

Puerto Rico and U.S. Virgin Islands

July 2023 was drier than normal across the U.S. Virgin Islands (USVI) and much of Puerto Rico (PR). The last 2-10 months were also drier than normal across most of PR and the USVI, with southern and eastern portions of PR near to wetter than normal. PR was wetter than normal at the 12-month time scale, while the USVI continued dry during this period. Drier-than-normal conditions dominated at longer time scales and became progressively more widespread (radar-based precipitation anomaly estimates for the last 1, 2, 3, 6, and 7 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).

In a 64-year record, Rohlsen Airport on St. Croix had the second driest December-July, eighth driest January-July, seventh driest February-July, and ninth driest July. In a 59-year record, King Airport on St. Thomas had the third driest December-July, fourth driest January-July, third driest February-July, and fifth driest July. In all of these rankings, years with too many days missing were excluded.

Temperatures were consistently warmer than normal, especially for the last 1 to 3 months (low elevation station temperature anomaly maps for the last 1, 2, 3, 4, 7, 10, 12 months). King Airport had the fifth hottest July and sixth hottest June-July, while Rohlsen Airport had the tenth hottest July and fifth hottest June-July (not counting years with too much missing data). The excessive heat increased evapotranspiration which made the dry conditions worse.

Root zone analyses indicated that soil conditions were moist across eastern coastal and portions of western PR, but dry along the southern and northern coasts and a strip across central PR (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, especially in the USVI. Monthly streamflow on PR showed below-normal streams in western and eastern areas. In the USVI, for the most part, groundwater steadily declined during July at St. Croix, St. John, and St. Thomas, although it temporarily rose slightly in response to beneficial rains near the end of the month at St. Thomas. For the most part, groundwater levels have been declining since the beginning of the year. The end-of-July groundwater level was well into the bottom third of the historical record on all three islands (St. Thomas, St. Croix, St. John).

In the USVI, drought conditions remained unchanged on St. Croix, where extreme drought continued, and St. John, where moderate drought continued, but extreme drought developed on St. Thomas. Moderate to severe drought expanded to cover about 8.6% of PR on the August 1, 2023 USDM map.

CONUS State Precipitation Ranks

July 2023 was drier than normal across most of the West, much of the northern and southern Plains, the Upper Mississippi Valley, and parts of the Gulf of Mexico Coast and interior Southeast, with record dryness occurring in parts of the West and northern Plains. Seventeen states had a precipitation rank in the driest third of the 129-year historical record for July, including five that ranked in the top ten driest category — Minnesota, Idaho, and Arizona (each third driest); New Mexico (fourth driest); and California (sixth driest) — and two that came close: North Dakota and Oregon (both 13th driest).

May-July 2023 was drier than normal across much of the Pacific Northwest, Southwest, and Mississippi Valley, and parts of the southern Plains and Ohio Valley to Mid-Atlantic region, with record dryness occurring in parts of the Pacific Northwest and Upper Mississippi Valley. Seventeen states had a precipitation rank in the driest third of the 1895-2023 historical record for May-July, including five that ranked in the top ten driest category — Wisconsin (fifth driest), Minnesota and Washington (both sixth driest), Arizona (eighth driest), and Iowa (ninth driest) — and one that came close: Louisiana (eleventh driest).

February-July 2023 was drier than normal across much of the Pacific Northwest, Southwest, Mississippi Valley, and Ohio Valley to Mid-Atlantic region, and parts of the southern Plains, with record dryness occurring in parts of the Southwest. Eleven states had a precipitation rank in the driest third of the historical record for February-July. None ranked in the top ten driest category, but one was close — Iowa (13th driest).

The year to date (January-July 2023) was drier than normal across much of the Pacific Northwest and Upper Mississippi Valley, and parts of the Southwest to southern Plains, Ohio Valley to Mid-Atlantic region, Gulf of Mexico Coast, and eastern sections of the central to northern Plains. Twelve states had a precipitation rank in the driest third of the historical record for January-July, including one that ranked in the top ten driest category — Maryland (tenth driest) — and one that came close: Washington (13th driest).

The last 12 months (August 2022-July 2023) were drier than normal across much of the Pacific Northwest, the Mid and Upper Mississippi Valley to eastern Great Plains, Ohio Valley to Mid-Atlantic region, and parts of the Southwest to southern Plains and Gulf of Mexico Coast. Twelve states had a precipitation rank in the driest third of the historical record for August-July. None ranked in the top ten driest category, but two were close — Washington (12th driest) and Kansas (13th driest).

Agricultural Belts

During July 2023, the Primary Corn and Soybean agricultural belt was drier than normal in northwest portions but wetter than normal to the east and south, with mostly cooler-than-normal temperatures. The month ranked as the 42nd wettest and 50th coolest July, regionwide, in the 1895-2023 record.

March marks the beginning of the growing season for the Primary Corn and Soybean agricultural belt. March-July 2023 was mostly drier than normal and near to warmer than normal. The period ranked as the 21st driest and 48th warmest March-July, regionwide.

The period April-June was especially dry for the Primary Corn and Soybean belt with temperatures mostly near to warmer than normal. The beneficial July precipitation did little to improve longer-term (April-July) moisture deficits. April-July 2023 ranked as the eleventh driest and 44th warmest April-July, regionwide.

According to the U.S. Department of Agriculture (USDA), as of August 1, 2023, drought affected approximately 22% of barley production, 57% of corn production, 20% of cotton production, 55% of sorghum production, 51% of soybean production, 44% of spring wheat production, 49% of winter wheat production, 30% of hay acreage, 37% of the cattle inventory, 29% of the milk cow inventory, and 31% of the sheep inventory. Based on July 30 USDA statistics, 15% of the nation's corn crop, 15% of the soybean crop, 31% of the cotton crop, 16% of the spring wheat crop, and 29% of the nation's pasture and rangeland were in poor to very poor condition, and 49% of the nation's topsoil and 49% of the subsoil were short or very short of moisture (dry or very dry). The table below lists the soil moisture, pasture and rangeland, corn, soybean, and spring 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), July 2023 was drier than normal in the Marshall Islands, northern Marianas, and part of the 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 Fananu (FSM) and Jaluit, Kwajalein, Majuro, and Wotje (Marshalls). July 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 July 2023, which is in the wet season for Palau, the Marianas, and most of the Marshalls and FSM, and in the dry season for American Samoa.

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

  • Saipan: July 2023 precipitation 4.13 inches, July normal mean 8.27 inches, July normal median 8.91 inches.
  • Guam: July 2023 precipitation 8.69 inches, July normal mean 12.14 inches, July normal median 10.14 inches.
  • Lukunor: July 2023 precipitation 11.89 inches, July normal mean 16.46 inches, July normal median 15.93 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 Aug
2022
Sep
2022
Oct
2022
Nov
2022
Dec
2022
Jan
2023
Feb
2023
Mar
2023
Apr
2023
May
2023
Jun
2023
Jul
2023
Aug-
Jul
Chuuk70%121%124%93%116%92%215%85%137%191%118%130%117%
Guam NAS62%109%150%77%182%350%188%263%198%916%146%86%135%
Kapingamarangi51%44%34%55%53%166%47%116%141%137%145%162%91%
Koror119%45%241%88%105%187%102%185%77%165%77%145%117%
Kosrae117%134%169%107%99%131%188%67%120%87%166%132%104%
Kwajalein132%68%161%81%88%224%50%189%188%345%143%45%125%
Lukonor32%36%95%94%54%124%68%96%77%61%116%75%66%
Majuro74%159%147%91%90%157%138%169%151%102%105%70%115%
Pago Pago121%60%149%118%71%114%110%106%152%168%109%102%101%
Pohnpei138%143%148%85%74%136%146%109%141%145%121%148%124%
Saipan80%67%151%60%130%441%118%138%192%225%92%46%109%
Yap65%57%217%68%131%133%118%137%104%131%121%168%115%
Pacific Island Precipitation (Inches)
Station Name Aug
2022
Sep
2022
Oct
2022
Nov
2022
Dec
2022
Jan
2023
Feb
2023
Mar
2023
Apr
2023
May
2023
Jun
2023
Jul
2023
Aug-
Jul
Chuuk8.98"14.15"14.27"9.83"13.00"9.34"15.60"7.09"17.14"21.57"13.73"15.56"160.26"
Guam NAS9.15"13.74"17.12"5.66"9.32"14.02"5.69"5.45"5.01"31.15"9.00"8.69"134"
Kapingamarangi4.17"4.38"2.76"5.11"5.23"15.23"4.37"13.24"19.19"16.59"20.04"22.86"133.17"
Koror16.00"5.26"28.49"10.00"11.76"19.04"8.74"13.74"5.60"19.53"13.44"26.81"178.41"
Kosrae16.69"19.11"18.53"14.74"15.95"21.87"24.25"10.81"21.08"15.41"24.30"19.67"222.41"
Kwajalein12.81"7.34"18.02"9.09"5.88"7.08"1.32"4.43"9.87"23.18"9.93"4.45"113.4"
Lukonor4.55"3.70"10.73"8.52"6.06"10.45"6.08"8.92"8.68"7.13"13.55"11.89"100.26"
Majuro8.65"17.72"18.76"12.21"10.30"12.14"9.51"11.12"14.23"10.35"11.56"7.87"144.42"
Pago Pago6.53"3.92"13.82"11.93"9.10"15.19"13.19"11.34"14.25"16.19"5.81"5.64"126.91"
Pohnpei19.69"17.91"22.62"12.66"11.86"17.94"13.99"14.29"25.90"29.02"17.94"22.76"226.58"
Saipan10.55"6.72"16.07"3.39"5.01"11.16"3.05"2.61"5.05"5.35"3.34"4.13"76.43"
Yap9.57"7.76"26.48"5.99"11.17"8.51"6.11"6.26"5.86"10.28"14.59"25.35"137.93"
Pacific Island 1981-2010 Normal Median Precipitation (Inches)
Station Name Aug
2022
Sep
2022
Oct
2022
Nov
2022
Dec
2022
Jan
2023
Feb
2023
Mar
2023
Apr
2023
May
2023
Jun
2023
Jul
2023
Aug-
Jul
Chuuk12.86"11.71"11.51"10.61"11.25"10.10"7.25"8.32"12.47"11.30"11.66"11.98"136.77"
Guam NAS14.74"12.66"11.44"7.38"5.11"4.01"3.03"2.07"2.53"3.40"6.18"10.14"99.09"
Kapingamarangi8.13"9.93"8.19"9.27"9.84"9.15"9.27"11.43"13.64"12.08"13.78"14.15"145.85"
Koror13.50"11.77"11.84"11.39"11.16"10.18"8.56"7.44"7.32"11.83"17.48"18.53"152.90"
Kosrae14.22"14.22"10.94"13.83"16.11"16.67"12.93"16.06"17.51"17.75"14.64"14.91"213.87"
Kwajalein9.74"10.74"11.18"11.28"6.66"3.16"2.64"2.35"5.26"6.72"6.93"9.87"90.41"
Lukonor14.04"10.15"11.32"9.08"11.27"8.41"8.93"9.26"11.31"11.69"11.65"15.93"151.36"
Majuro11.69"11.17"12.73"13.44"11.39"7.74"6.88"6.58"9.42"10.11"11.01"11.17"125.25"
Pago Pago5.38"6.53"9.26"10.14"12.84"13.34"12.00"10.68"9.39"9.66"5.33"5.55"125.57"
Pohnpei14.26"12.55"15.27"14.83"16.08"13.18"9.55"13.17"18.41"19.96"14.81"15.43"182.36"
Saipan13.13"10.09"10.62"5.61"3.85"2.53"2.59"1.89"2.63"2.38"3.62"8.91"70.25"
Yap14.82"13.50"12.18"8.83"8.51"6.39"5.19"4.56"5.63"7.85"12.04"15.08"120.31"

As measured by percent of normal precipitation, Lukunor was drier than normal in the short term (July and the last 3 months [May-July]) and long term (year to date [January-July] and last 12 months [August 2022-July 2023]). Majuro and Saipan were drier than normal in the short-term but wetter than normal in the long-term. Guam and Kwjalein were drier than normal for July but wetter than normal for the other 3 time periods. Kapingamarangi was drier than normal at the 12-month time scale, but wetter than normal for the other 3 time scales. Airai, Chuuk, Kosrae, Pago Pago, Pohnpei, and Yap were near to wetter than normal for all 4 time periods.

Based on percent of normal average (instead of normal median values), in the Marianas Islands, precipitation was drier than normal across the main islands in July and across most of the islands for June-July. The last 3 months were wetter than normal over Guam and drier than normal over the islands to the north. The last 4 to 24 months were mostly above normal across the main islands. Longer time periods had a mixed anomaly pattern but were mostly above normal (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, July and June-July were drier than normal across most of the islands. The last 3 to 4 months were drier than normal at Jaluit and Kwajalein. Longer time periods were drier than normal in the southwest (Jaluit) with wetter-than-normal conditions across the rest of the RMI stations, except the last 60 months where the northern stations and southwestern stations were drier than normal (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 July 31 USDM produced for the USAPI, Fananu, Kwajalein, and Wotje were abnormally dry with the rest of the USAPI stations free of drought and abnormal dryness. The reservoir level on Majuro began the month at its highest level (29.4 million gallons), decreased to a low value of 25.9 million gallons on July 20, then increased again to end the month at 28.8 million gallons. The threshold of concern for drought is usually 28.8 million gallons, but for the past several months, one sector of the reservoir has been serviced. This portion of the reservoir system typically holds 8 million gallons, so the threshold reservoir level is lower than it normally would be. The minimum value reached during this month was above the new threshold for concern. Satellite observations of vegetative health (drought stress, stressed vegetation, VHI) indicated there were some areas of stressed vegetation on Guam.

July 2023 precipitation ranks ranged from very dry to very wet, based on data available at the time of this report. Jaluit, Kwajalein, Majuro, and Saipan had July precipitation that ranked in the top ten driest category, while Airai, Mili, Pohnpei, Ulithi, and Yap ranked in the top ten wettest category, and Kapingamarangi had the wettest July on record:

  • Kwajalein: second driest July (in a 72-year record).
  • Jaluit: third driest July (40 years) and fifth driest August-July.
  • Saipan: fourth driest July (43 years) and seventh driest June-July.
  • Majuro: ninth driest July (70 years).
  • Kapingamarangi: wettest July (34 years), but still the tenth driest rank for August-July.

Other stations at the wet end of the scale:

  • Ulithi had the fourth wettest July (39 years).
  • Yap ranked third wettest for July (73 years).
  • Mili had the eighth wettest July (38 years) but wettest June-July, May-July, and January-July through August-July.

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 July 2023, February-July 2023 (last 6 months), and August 2022-July 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.

July 2023 USAPI Precipitation Ranks (1 = driest)
StationJuly 2023Feb-Jul 2023Aug 2022-Jul 2023Period of Record
RankYearsRankYearsRankYears
Ailinglaplap1139343932361981-2023
Airai6673637266711951-2023
Chuuk5773677260721951-2023
Fananu28--3--32003-2023
Guam2067666663661957-2023
Jaluit3407395371981-2023
Kapingamarangi3434252710201962-2023
Kosrae4155294524361954-2023
Kwajalein272527160711952-2023
Lukunor11396392261981-2023
Majuro970446950691954-2023
Mili3138373835351981-2023
Nukuoro2540273930381981-2023
Pago Pago2858435731571966-2023
Pingelap11392038--341981-2023
Pohnpei6473677269721951-2023
Saipan443224227341981-2023
Ulithi3639323821351981-2023
Utirik--16--8--41985-2020
Woleai2542--33--281968-2023
Wotje2739323929361981-2023
Yap7173637257721951-2023
Map of USAPIJuly 2023 Precipitation (Inches)
Map of USAPI July 2023 Percent of Normal Precipitation
Map of USAPI May 2023-July 2023 Percent of Normal Precipitation
Map of USAPI January-July 2023 Percent of Normal Precipitation
Map of USAPI August 2022-July 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, mean temperatures were above average across much of the Southeast region in July and, as is often the case during the summer, precipitation was variable across the region this month. The driest locations were found across central portions of Georgia and the Carolinas as well as the West Coast of Florida, where monthly precipitation ranged from 2 to 5 inches (51 to 127 mm) below average (33 to 75 percent of normal), with a few locations recording less than a quarter of their normal monthly amount. Sarasota, FL (1911-2023) recorded its second driest July on record with 1.1 inches (28 mm) of precipitation, which is only 12 percent of normal.

Mean temperatures were above average across Puerto Rico and the U.S. Virgin Islands and monthly precipitation was below average across much of Puerto Rico and the U.S. Virgin Islands. Cyril King Airport on the island of Saint Thomas tied its fifth driest July on record (since 1953) with just 0.81 inch (21 mm) of precipitation, while Henry Rohlsen Airport on Saint Croix recorded 1.26 inches of precipitation (32 mm), which is a little less than half of normal.

The greatest improvements in the USDM were observed across northern Alabama and northern and central portions of Virginia, where only small areas of moderate (D1) drought remained by the end of the month. Small pockets of abnormal dryness (D0) were also eliminated across the state of Georgia. On the other hand, moderate (D1) drought emerged across extreme southwestern Virginia, while small pockets of abnormal dryness (D0) emerged across the Carolinas. Hot and dry conditions during the month resulted in a two-category degradation along the West Coast of Florida, with severe (D2) and extreme (D3) drought emerging in Pinellas and Hillsborough counties. Overall, by the end of the month, only about 6 percent of the region was at least abnormally dry, which is the lowest percentage since September 2021. In the Caribbean, severe (D2) drought expanded across northwest Puerto Rico. Abnormal dryness (D0) persisted across the southern and northern slopes but contracted over the eastern part of the island. Severe (D2) drought emerged on Saint John, while extreme (D3) drought emerged on Saint Thomas. Conditions on Saint Croix improved from exceptional (D4) to extreme (D3) drought by the end of the month.

South

As explained by the Southern Regional Climate Center, above-normal temperatures were prevalent in the southern portions of the region during July, with areas from far west Texas to the Gulf Coast of Mississippi ranging from two to six degrees above normal. A persistent heat wave in Texas and Louisiana led to several fatalities and a high number of emergency room visits during the month. In the northern portions of the region, near normal temperatures were common, generally between two degrees below and two degrees above normal. Precipitation was below normal for the southern portions of the region, with the largest departures across central and western Texas. Precipitation was generally above normal for the northern portions of the region, with some locations in western Oklahoma and the Texas Panhandle exceeding 300 percent of normal precipitation. Between the two extremes in regional totals, the Southern region as a whole was near its historical median value for precipitation.

During July, the Southern region saw improvement of drought conditions across the Texas Panhandle, much of Oklahoma, northern Arkansas, northern Mississippi, and much of Tennessee. Some regions of Oklahoma saw as many as three classes of improvement according to the USDM. In the southern portions of the region degradation of drought status was common, particularly in far west Texas and central Texas where some areas saw as much as three categories of degradation. Areas experiencing extreme or exceptional drought remained confined to central Texas and north-central Oklahoma. Much of the Texas Panhandle, northeastern Texas, Oklahoma, Arkansas, Tennessee, Mississippi, and northern Louisiana remained free of drought as of July 25th. Drought conditions, combined with little rain, and hot temperatures have led to short to very short topsoil moisture conditions across much of Texas and have negatively impacted the state's cotton crop, with only 17 percent of Texas cotton being reported to be in good to excellent condition as of July 30th. In contrast to dry conditions across Louisiana and Texas, heavy rain events throughout the month led to reports of flash flooding events in Oklahoma, Arkansas, Mississippi, and Tennessee.

Midwest

As described by the Midwest Regional Climate Center, July precipitation totaled 4.34 inches (110 mm) for the Midwest, which was 0.24 inch (104 mm) above normal, or 106 percent of normal, while the average July temperature for the Midwest was 72.3 degrees F (22.4 degrees C), which was 0.5 degrees F (0.3 degrees C) below the 1991-2020 normal. Precipitation was near to above normal east of the Mississippi River and below normal to the west, with mixed conditions in Missouri.

About 83 percent of the Midwest was abnormally dry or in drought in late July. Drought conditions improved throughout the month along and east of a line from southeast Missouri to Michigan. Heavy rainfall resulted in a rare 2-category improvement on the USDM map from July 11 to July 18 across northern Illinois, southern Michigan, western Indiana, and eastern Missouri. Drought persisted or intensified across Minnesota, Wisconsin, and northern Missouri. By month's end, 71 percent of pasture and rangeland and 44 percent of corn crops were rated poor to very poor in Missouri. Topsoil moisture was short to very short on 61-76 percent of cropland west of the Mississippi River.

Northeast

As summarized by the Northeast Regional Climate Center, the Northeast had its seventh warmest July since records began in 1895 with an average temperature of 72.5 degrees F, 2.3 degrees F above normal, and the fourth wettest July, 141 percent of normal. This July ranked as the warmest on record for Maine and among the 10 warmest Julys for nine additional states.

The USDM from July 4 showed 1 percent of the Northeast in severe drought, 19 percent in moderate drought, and 41 percent as abnormally dry. Multiple parts of the Northeast had excessively wet conditions during July, alleviating drought and dryness but also, in some locations, causing flash flooding. Severe drought eased in south-central Pennsylvania and shrank in coverage in central Maryland. Meanwhile, moderate drought was erased from Vermont and Connecticut and contracted in New York, Pennsylvania, New Jersey, Maryland, and West Virginia. Additionally, abnormal dryness eased in Vermont, Massachusetts, and Delaware, and contracted in the rest of the Northeast. The USDM from August 1 showed 1 percent of the Northeast in severe drought, 3 percent in moderate drought, and 11 percent as abnormally dry. Heavy rain during July boosted streamflow for most areas. The main exceptions were parts of eastern West Virginia, central Maryland, south-central Pennsylvania, and western New York, which generally saw less precipitation and continued to report below-normal flows. Similarly, record low groundwater levels were found in areas such as eastern West Virginia, central Maryland, south-central Pennsylvania, and eastern New Jersey at times during the month.

High Plains

As summarized by the High Plains Regional Climate Center, July was a mixed bag of weather for the High Plains. Precipitation was greatly needed for some, while others received next to nothing. Cooler temperatures dominated much of the region, despite a heatwave late in the month.

Aside from scattered pockets of above-normal precipitation, the region was fairly dry this month. Western Colorado and the majority of North Dakota were well below normal, with places of near-record dryness. While eastern Colorado has received normal to above normal precipitation these past few months, the western part of the state has not been so lucky. Grand Junction tied with 1898 for the driest on record, while Alamosa was the driest. Next to zero precipitation occurred in both places this month and combined with the recent heat, drought conditions have begun to be reintroduced in the southwestern part of the state. Among those who missed the rain this month include McCook, Nebraska, and the surrounding area. Just a few months ago, they recorded their wettest month ever by a large margin and greatly improved the ongoing drought. This month was a setback, as only 0.50 inch (12.7 mm) precipitation occurred, and it was ranked 5th driest. At the end of June, they ranked 10th wettest for January through June period. Currently, they rank 25th after a meager July precipitation.

West

As summarized by the Western Regional Climate Center, July brought prolonged periods of extreme heat to the Southwest with record warmth at many locations. This was partially due to the delayed onset of the Southwest monsoon as the semi-permanent summer sub-tropical high-pressure center was shifted further south than normal with little moisture making it into the core of the monsoon region: Arizona and New Mexico. Outside of the southwest temperatures were above normal and precipitation below normal across much of the West.

The lack of monsoon rains across the Southwest brought decreased cloud cover, lower humidities, a drier and hotter land surface, and extreme heat with record high mean monthly temperatures over large areas of Arizona and New Mexico. Parts of California and Nevada also saw record temperatures. July is typically one of the wettest months of the year in Arizona and New Mexico due to the onset of the monsoon but little precipitation, and in some cases no measurable precipitation, fell this year. For the first time since records began in 1892, there was no measurable precipitation in Albuquerque, New Mexico where normal July precipitation is 1.64 inches; several days with trace amounts of precipitation did occur. Southwest New Mexico was also extremely dry with Hillsboro (0.03 inch and 1 percent of normal) and Redrock (0.35 inch and 13 percent of normal) also saw record low July precipitation totals. Flagstaff, Arizona logged just 0.71 inch of precipitation (27 percent of normal) coming in as the ninth driest July on record. Most of California and Oregon saw no precipitation in July and precipitation was below normal across the entire Pacific Northwest with many locations seeing 0-50 percent of normal.

According to the USDM at the end of July, 21 percent of the West was in drought. Drought conditions have worsened over Arizona, New Mexico, southwest Colorado, and southeast Utah due to a lackluster start to the monsoon season with little precipitation in July. Several areas of severe drought (D2) can be found in New Mexico. Drought also expanded across the Pacific Northwest with D2 condition in Oregon, Washington, Idaho, and Montana.

Alaska: Temperatures across Alaska were above normal except for areas of the southwest part of the state, where temperatures were 1-2 degrees Fahrenheit below normal. Record July warmth was found in the middle and upper Yukon Basins where temperatures were generally 3-6 degrees Fahrenheit above normal. Precipitation was above normal for much of south-central, western, and the North Slope of Alaska with below normal precipitation for the Interior and Panhandle. On the Panhandle, Yakutat had a record dry July with 1.14 inches of precipitation (15 percent of normal) and Juneau saw its fourth driest July with 1.79 inches of precipitation (35 percent of normal).

Hawaii: Across Hawaii, precipitation was below normal and temperatures were near-to-above normal. Hana had its driest July since records began in 1951 with 2.34 inches of precipitation (43 percent of normal). On the Big Island, Hilo received 4.97 inches of precipitation (54 percent of normal) in July, making it the tenth driest on record. Temperature-wise, Lihue had its warmest July on record at 81.9 degrees Fahrenheit (2.3 degrees Fahrenheit above normal) and Molokai had its sixth warmest July at 79.4 degrees Fahrenheit (0.3 degrees Fahrenheit above normal). Maui is currently the only island with drought conditions present where much of the island is in moderate drought (D1) with a small area on the western shores in severe drought (D2).

Additional Resources


Citing This Report

NOAA National Centers for Environmental Information, Monthly Drought Report for July 2023, published online August 2023, retrieved on June 14, 2024 from https://www.ncei.noaa.gov/access/monitoring/monthly-report/drought/202307.