Issued 11 May 2023

April 2023 Palmer Z-Index
U.S. Percent Area Wet or Dry January 1996 - April 2023
April 2023 /monitoring-content/sotc/drought/2023/04/reg111dv00elem01-05042023.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

  • A file containing the national monthly percent area severely dry and wet from 1900 to present is available for the severe to extreme and moderate to extreme categories.
  • Historical temperature, precipitation, and Palmer drought data from 1895 to present for climate divisions, states, and regions in the contiguous U.S. are available at the Climate Division: Temperature-Precipitation-Drought Data page. These filenames begin with "climdiv".
  • U.S. Drought Monitor information is currently unavailable.

Detailed Drought Overview

The atmospheric circulation over North America continued to be very active during April 2023. Numerous upper-level shortwave troughs and closed lows moved through the jet stream flow throughout the month, dragging Pacific fronts and surface lows with them. The favored areas for these weather systems shifted throughout the month, creating and reflecting what is called a long-wave trough in the jet stream flow that shifted back and forth across the CONUS. A compensating long-wave ridge shifted in tandem with the trough. When averaged across the month, these competing migrating features resulted in a fairly flat monthly circulation pattern (or zonal flow) across the CONUS, with the hint of an anomalous trough in the central part of the country and anomalous ridges over the Northeast and edging into the Southwest. The cold fronts and surface lows spread above-normal precipitation over coastal parts of the Pacific Northwest and over parts of the Upper Mississippi Valley and Great Lakes. They tapped Gulf of Mexico and Atlantic moisture to bring above-normal precipitation to southern and eastern parts of Texas, the Lower Mississippi Valley, and Florida northward to Virginia. But drier-than-normal weather dominated most of the West and Great Plains to the Ohio Valley, and parts of the Mid-Atlantic to New England. A mixed precipitation anomaly pattern occurred over Alaska, Puerto Rico, and the U.S. Virgin Islands, while Hawaii had a wetter-than-normal month. The monthly temperature anomaly pattern reflected the anomalies in the monthly circulation, with colder-than-normal temperatures over much of the West and Plains, and warmer-than-normal temperatures over the Great Lakes to Northeast, along the Atlantic and Gulf coasts, and into the Southwest. The warmest temperature anomalies occurred in the Northeast, where near-record warmth occurred.

The above-normal precipitation resulted in contraction or reduction of the intensity of drought over parts of the Gulf and Atlantic coasts. Even though April precipitation was mostly below normal, melting of an above-normal winter-spring snowpack in the northern Plains, Upper Midwest, and West contributed to contraction or reduction of the intensity of drought in those areas. Other areas experiencing a drier-than-normal month saw drought expansion or intensification. These areas included parts of the Great Plains, Mid-Mississippi Valley, and southern New England. Drought contraction exceeded expansion with the USDM-based national moderate-to-exceptional drought footprint across the CONUS decreasing from 28.2% at the end of March to 24.4% at the end of April (from 23.6% to 20.4% for the 50 states and Puerto Rico).

According to the Palmer Drought Index, which goes back to the beginning of the 20th century, about 14.6% of the CONUS was in moderate to extreme drought at the end of April, which is a decrease compared to the end of March.

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Drought conditions at the end of April, as depicted on the May 2, 2023 USDM map, included the following core drought and abnormally dry areas:

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.

April 2023 Palmer Z-Index
April 2023 PHDI

Used together, the Palmer Z Index and PHDI maps show that short-term drought occurred in the central to southern Great Plains, expanding or intensifying long-term drought (PHDI maps for April compared to March), and in Maine, the Mid-Mississippi Valley to southern Great Lakes, and parts of California, eliminating or reducing the intensity of long-term wet conditions. Short-term wet conditions occurred in parts of the Pacific Northwest, coastal Texas, southern Florida, the Carolinas, and the Mid-Atlantic coast, reducing the intensity of long-term drought, and in the western Great Lakes, intensifying long-term wet conditions.

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.

April 2023 SPI
March-April 2023 SPI
February-April 2023 SPI
November 2022-April 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 the central Plains and parts of the southern Plains at all time scales, and is especially widespread and intense at the 1- to 3- and 9- to 24-month time scales. Parts of the northern Plains are dry at 1 to 3, 9, and (in the Montana Plains) 24 months. The Southwest (from California to Colorado and New Mexico) is dry at the 1-month time scale, but mostly wet at 2 to 12 months. The Mid-Mississippi Valley is dry at 1 to 2 months, and parts of this region are dry at 12 to 24 months. The central Appalachians have dryness at the 1- to 6-month time scales. The Mid-Atlantic region (North Carolina to New Jersey) is dry at 9 to 24 months. Maine is dry at 1 and 3 months. The Pacific Northwest has dryness in some parts at 9 and 24 months, and parts of the northern Rockies are dry at all time scales. Parts of Florida are dry at 3 to 12 months, while southern Louisiana has dryness at 2 to 3 months. Much of the West is wet at 2 to 12 months, with parts of California and the Southwest wet even at 24 months. Parts of the Great Lakes are wet at all time scales. Coastal and east Texas are wet at 1 to 6 months, with the wet region shifting eastward to the Lower Mississippi and Tennessee valleys at 6 to 24 months. At the 24-month time scale, it is wet from the central Gulf of Mexico Coast to the Great Lakes and New England.

August 2022-April 2023 SPI
May 2022-April 2023 SPI
May 2021-April 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, April is in the middle of climatological spring, which is the season when evapotranspiration is increasing with rising sun angle and longer days. During April 2023, temperatures were warmer than normal across the East Coast and into the Great Lakes, but most of the CONUS averaged near to cooler than normal. The core drought area (Great Plains) and areas that were drier than normal in April (Great Plains, Southwest, and Mid-Mississippi Valley) had mostly near-normal temperatures, so evapotranspiration was not a major factor. For most of the last 12 months, temperatures have been cooler than normal in the West and warmer than normal in the East (temperature anomaly maps for the last 1, 3, 4, 6, 9, 12 months), so the SPI and SPEI values in the central and western drought areas were comparable in magnitude — the SPI was even greater than the SPEI at the 1-, 3-, and 9-month time scales (SPEI maps for the last 1, 3, 6, 9, 12 months) (SPI maps for the last 1, 3, 6, 9, 12 months).

The last ten to 20 years have been a period of unusually warm temperatures across the West, especially during the warm half of the year (April-September) but also during the cold half of the year (October-April) (this year has seen a return to cooler temperatures). There have also been periods of extreme dryness westwide during this period (this year also being an exception for precipitation). The combination of excessive heat and dryness has resulted in more extreme SPEI values than SPI values for the last six years (SPEI maps for last 24, 30, 36, 48, 60, 72 months) (SPI maps for last 24, 30, 36, 48, 60, 72 months).

Near-normal temperatures for the last 9 months inhibited the magnitude of the SPEI for Kansas, resulting in a 9-month SPI that was more extreme than the corresponding SPEI.

The excessive heat in the southern Plains during recent summers and in the West for the last several years gave Texas and California more extreme SPEI values than SPI values at longer (multi-year) time scales:

Regional Discussion

Western United States

The precipitation anomaly pattern for April 2023 was the reverse of what it has been for much of the water year (October-present) — the Pacific Northwest was wetter than normal this month while most of the rest of the West was drier than normal. The low precipitation in April resulted in some drying of surface soils, but deeper soils were still moist (soil moisture maps 1, 2, 3, 4, 5, 6), and melting of the record to near-record mountain snowpack fed rivers and streams and maintained inflow to reservoirs.

For the West as a whole, April 2023 ranked as the 39th driest and 54th coolest April in the 1895-2023 record. October-April ranked 30th wettest and 30th coolest, while the last 12 months were the 24th wettest and 45th warmest May-April in the 129-year record. Conditions are drier and hotter at longer time scales: the last 24 months ranked as the 68th driest and 13th warmest such 24-month May-April period, and the last 36 months ranked as the 18th driest and eighth warmest such 36-month May-April period.

Based on the USDM, the percent area of the western U.S. in moderate to exceptional drought fell to 25.2% at the end of April. Based on the Palmer Drought Index, about 2.6% of the western U.S. was experiencing moderate to extreme drought at the end of April. This is a decrease compared to the end of March, is based on the Palmer Drought Severity Index (PDSI), and reflects the impact of this winter's wet circulation pattern. The PDSI is a meteorological drought index. The Palmer Hydrological Drought Index (PHDI) is a hydrological drought index that reflects hydrological conditions instead of changes in atmospheric circulation. The PHDI shows a little more drought remaining across the West than does the PDSI. Since the Palmer data go back to the beginning of the 20th century, they show that the last two decades have had a greater spatial extent of persistent drought in the West than any other decades in the last 123 years.

Great Plains

The central and southern Great Plains have experienced persistently drier-than-normal weather for the last 1 to 12 months and beyond, extending to the last 2 to 3 years (percent of normal precipitation maps for the last 1, 2, 3, 6, 9, 12, 24, 36, 48, 60 months). The dry weather has been accompanied by unusually warm temperatures. The persistent warmth has dominated much of the last two decades. Regionwide, the Great Plains had the 12th driest and 39th coolest April in the 1895-2023 record, the 17th driest and 33rd warmest May-April 12-month period, the 16th driest and 13th warmest May-April 24-month period, and the ninth driest and 12th warmest May-April 36-month period.

The combination of heat and dryness over the last 30 months has given some parts of the central and southern Plains near-record extreme SPEI values:

For the Nebraska areas, the April 2023 30-month SPEI is as extreme as the drought of the 1930s, and for the Texas areas, the April 2023 30-month SPEI is as extreme as the drought of the 1950s.

As of the end of April, 41.8% of the Great Plains region was affected by moderate to extreme drought, based on the PDSI. This is about the same as the end of March. The recent drought, at its peak last year, was as expansive as the drought of the 1950s.

Hawaii

Wetter-than-normal conditions dominated the Hawaiian Islands in April and for the last 1 to 9 months, except for some dryness on the windward side of the Big Island and southern portions of Oahu. Drier-than-normal conditions were more extensive on the Big Island and Oahu at 12-24 and 48 months and spread to Maui and Molokai at 36 months. A mixed pattern was 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 on Maui and the Big Island but near to above normal on Molokai, Oahu, and Kauai. Based on satellite analyses (stressed vegetation, drought stress, VHI), there were a few areas of vegetative stress this month on Maui and the Big Island, but little to no stress elsewhere.

A small (2.4%) area of moderate drought developed on the Big Island while abnormal dryness and drought shrank to cover 3.8% of Hawaii, as seen on the May 2, 2023 USDM map.

Alaska

April 2023 was drier than normal across the Aleutians and Northwest Gulf to Cook Inlet regions of Alaska, and in parts of western and northern Alaska. The dryness was mostly limited to the southern coastal areas at 2-7 months. At the 12-month time scale, it was drier than normal at Aleutian and Northwest Gulf stations and some locations in the panhandle and the east-central region. The dry precipitation anomalies were mostly centered around the Northwest Gulf-Cook Inlet area 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 basin percent of normal precipitation maps for the last 7 months) (high elevation SNOTEL station precipitation percentile maps for the last 1 and 7 months) (SNOTEL basin and station percent of normal precipitation maps for the last 1 and 7 months) (climate division precipitation rank maps for the last 1, 3, 4, 6, and 12 months) (climate engine model percent of normal precipitation map for the last month) (Leaky Bucket model precipitation percentile map).

April temperatures were cooler than normal statewide. Temperatures were near to below normal in most areas at the 2- to 3-month time scales. Warmer-than-normal temperatures were evident in the north coastal and south coastal areas at 4 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, 4, 7, 12 months) (climate division temperature rank maps for the last 1, 3, 4, 6, and 12 months) (gridded temperature percentile maps for the last 1, 3, and 4 months) (Leaky Bucket model temperature percentile map).

With topsoil temperatures still below freezing across most of the state, the winter snowpack covered the state and was near to above average in most basins. Snow water content (SWE) was near to above normal except for some SNOTEL stations in the south central area (satellite-based estimates of snow depth and SWE; SNOTEL station SWE percentile; SNOTEL basin percent of normal SWE; SNOTEL station and basin percent of normal SWE). For those streams that were not frozen, monthly streamflow was below normal on the Kenai Peninsula and near to above normal in the panhandle.

Alaska was free of drought and abnormal dryness on the May 2, 2023 USDM map.

Puerto Rico and U.S. Virgin Islands

April 2023 and the last 2 to 7 months were drier than normal across northwestern parts of Puerto Rico (PR) and most of the U.S. Virgin Islands (USVI). It was mostly wetter than normal over both territories at 9 to 10 months. The USVI were drier than normal at 12 to 24 months with a mixed anomaly pattern over PR. Drier-than-normal conditions dominated both at longer time scales (radar-based precipitation anomaly estimates for the last 1, 2, 3, 4, and 6 months) (low elevation station precipitation 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).

Root zone analyses indicated that soil conditions were moist across northeastern and interior portions of PR, but dry along the southern and northwest coasts of PR (root zone soil saturation fraction); satellite-based analyses indicated that top layers of the soil were dry across the USVI and western and northern PR, and deeper soils were drying out (relative soil moisture at 0-10 cm [0-4 in], 10-40 cm [4-16 in], 40-100 cm [16-39 in], 100-200 cm [39-79 in] depth). Satellite analyses showed a few areas of vegetative stress due to drought (VHI for PR and USVI, drought stress for PR and USVI, stressed vegetation for PR and USVI). Monthly streamflow on PR showed a few below-normal streams in the west with near to above-normal streams in other areas. In the USVI, for the most part, groundwater steadily declined during April at St. Croix and St. John, and rose then declined at St. Thomas. The end-of-April groundwater level was in mid-range (below previous peaks and above recent low levels) on all three islands (St. Thomas, St. Croix, St. John).

In the USVI, severe drought continued on St. Croix, moderate drought continued on St. Thomas, and abnormal dryness continued on St. John. Moderate drought shrank to cover about 18.1% of PR on the May 2, 2023 USDM map.

CONUS State Precipitation Ranks

April 2023 was drier than normal from California to the Great Plains, across much of the Ohio and Tennessee Valleys, and parts of the Northeast, with record dryness occurring in the Southwest and parts of Nebraska. Eighteen states had a precipitation rank in the driest third of the 129-year historical record for April, including four that ranked in the top ten driest category — Arizona (third driest), Missouri (fourth driest), Nebraska (fifth driest), and New Mexico (sixth driest) — plus one that was close — Nevada (11th driest).

February-April 2023 was drier than normal across most of the Great Plains, much of the Northeast, and parts of the Pacific Northwest and Gulf of Mexico coast. Eleven 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 — Nebraska (fourth driest) and Maine (eighth driest). Western parts of Texas and Oklahoma were much drier than normal, but eastern parts were wetter than normal, which put those states into the middle third of the historical record.

The year to date (January-April 2023) was drier than normal across much of the Great Plains and parts of the Pacific Northwest, Mid-Atlantic coast, and Gulf of Mexico coast. Eight 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 — Maryland (13th driest).

The last six months (November 2022-April 2023) were drier than normal across the southern to central Plains and parts of the Pacific Northwest, Gulf of Mexico coast, and Atlantic coast. Five states had a precipitation rank in the driest third of the historical record, but none ranked in the top ten driest category or were even close.

The last 12 months (May 2022-April 2023) were drier than normal across much of the Great Plains and parts of the Pacific Northwest, Atlantic coast, and Gulf of Mexico coast. Seven states had a precipitation rank in the driest third of the historical record, including one that ranked in the top ten driest category — Nebraska (fourth driest).

Agricultural Belts

During April 2023, the Primary Hard Red Winter Wheat agricultural belt was mostly drier than normal with monthly temperatures that were mostly near average. The month ranked as the 19th driest and 57th warmest April, regionwide, in the 1895-2023 record.

October marks the beginning of the growing season for the Primary Hard Red Winter Wheat belt. October 2022-April 2023 was mostly drier than normal with cooler-than-normal temperatures in the north and near-normal temperatures in the south. The period ranked as the 28th driest and 49th warmest October-April, regionwide, on record.

During April 2023, the Primary Corn and Soybean agricultural belt was mostly drier than normal and slightly warmer than normal. The month ranked as the 35th driest and 53rd warmest April, regionwide, in the 1895-2023 record.

March marks the beginning of the growing season for the Primary Corn and Soybean agricultural belt. March-April 2023 was wetter than normal in the southeast and drier than normal elsewhere, with temperatures that were colder than normal everywhere except in the far east and south. The period ranked as the 64th driest (66th wettest) and 59th warmest March-April, regionwide, in the 1895-2023 record.

According to the U.S. Department of Agriculture (USDA), as of May 2, 2023, drought affected approximately 6% of barley production, 27% of corn production, 38% of cotton production, 77% of sorghum production, 20% of soybean production, 13% of spring wheat production, 49% of winter wheat production, 25% of hay acreage, 41% of the cattle inventory, 13% of the milk cow inventory, and 25% of the sheep inventory. Based on April 30 USDA statistics, 42% of the nation's winter wheat crop was in poor to very poor condition, and 28% of the nation's topsoil and 33% of the subsoil were short or very short of moisture (dry or very dry). The table below lists the soil moisture 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 winter wheat in poor or very poor condition, highlighted in yellow:

Statewide topsoil moisture, subsoil moisture, and crop condition

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), April 2023 was drier than normal in the Republic of Palau and parts of the FSM, and near to wetter than normal everywhere else.

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 (RMI); Airai (ROP); and Ulithi and Yap (FSM). April 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 April 2023, which is in the wet season for the eastern and southern FSM and dry season for the rest of Micronesia. Precipitation was below the monthly minimum but above normal (1981-2010 normal), because the normals are low, at:

  • Yap: April 2023 precipitation 5.86 inches, April normal mean 5.72 inches, April normal median 5.63 inches.

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

  • Lukunor: April 2023 precipitation 8.68 inches, April normal mean 11.86 inches, April normal median 11.31 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 May
2022
Jun
2022
Jul
2022
Aug
2022
Sep
2022
Oct
2022
Nov
2022
Dec
2022
Jan
2023
Feb
2023
Mar
2023
Apr
2023
May-
Apr
Chuuk176%68%107%70%121%124%93%116%92%215%85%137%110%
Guam NAS69%79%135%62%109%150%77%182%350%188%263%198%107%
Kapingamarangi10%25%61%51%44%34%55%53%166%47%116%141%60%
Koror203%81%72%119%45%241%88%105%187%102%185%77%111%
Kosrae132%139%169%117%134%169%107%99%131%188%67%120%108%
Kwajalein196%141%94%132%68%161%81%88%224%50%189%188%119%
Lukonor88%62%66%32%36%95%94%54%124%68%96%77%63%
Majuro66%71%96%74%159%147%91%90%157%138%169%151%112%
Pago Pago96%110%166%121%60%149%118%71%114%110%106%152%98%
Pohnpei112%122%173%138%143%148%85%74%136%146%109%141%123%
Saipan76%106%159%80%67%151%60%130%441%118%138%192%119%
Yap153%83%110%65%57%217%68%131%133%118%137%104%105%
Pacific Island Precipitation (Inches)
Station Name May
2022
Jun
2022
Jul
2022
Aug
2022
Sep
2022
Oct
2022
Nov
2022
Dec
2022
Jan
2023
Feb
2023
Mar
2023
Apr
2023
May-
Apr
Chuuk19.87"7.93"12.86"8.98"14.15"14.27"9.83"13.00"9.34"15.60"7.09"17.14"150.06"
Guam NAS2.35"4.88"13.71"9.15"13.74"17.12"5.66"9.32"14.02"5.69"5.45"5.01"106.1"
Kapingamarangi1.19"3.40"8.60"4.17"4.38"2.76"5.11"5.23"15.23"4.37"13.24"19.19"86.87"
Koror24.06"14.19"13.31"16.00"5.26"28.49"10.00"11.76"19.04"8.74"13.74"5.60"170.19"
Kosrae23.42"20.39"25.14"16.69"19.11"18.53"14.74"15.95"21.87"24.25"10.81"21.08"231.98"
Kwajalein13.17"9.78"9.23"12.81"7.34"18.02"9.09"5.88"7.08"1.32"4.43"9.87"108.02"
Lukonor10.27"7.19"10.52"4.55"3.70"10.73"8.52"6.06"10.45"6.08"8.92"8.68"95.67"
Majuro6.72"7.78"10.70"8.65"17.72"18.76"12.21"10.30"12.14"9.51"11.12"14.23"139.84"
Pago Pago9.32"5.84"9.23"6.53"3.92"13.82"11.93"9.10"15.19"13.19"11.34"14.25"123.66"
Pohnpei22.32"18.02"26.66"19.69"17.91"22.62"12.66"11.86"17.94"13.99"14.29"25.90"223.86"
Saipan1.81"3.84"14.16"10.55"6.72"16.07"3.39"5.01"11.16"3.05"2.61"5.05"83.42"
Yap12.04"10.04"16.54"9.57"7.76"26.48"5.99"11.17"8.51"6.11"6.26"5.86"126.33"
Pacific Island 1981-2010 Normal Median Precipitation (Inches)
Station Name May
2022
Jun
2022
Jul
2022
Aug
2022
Sep
2022
Oct
2022
Nov
2022
Dec
2022
Jan
2023
Feb
2023
Mar
2023
Apr
2023
May-
Apr
Chuuk11.30"11.66"11.98"12.86"11.71"11.51"10.61"11.25"10.10"7.25"8.32"12.47"136.77"
Guam NAS3.40"6.18"10.14"14.74"12.66"11.44"7.38"5.11"4.01"3.03"2.07"2.53"99.09"
Kapingamarangi12.08"13.78"14.15"8.13"9.93"8.19"9.27"9.84"9.15"9.27"11.43"13.64"145.85"
Koror11.83"17.48"18.53"13.50"11.77"11.84"11.39"11.16"10.18"8.56"7.44"7.32"152.90"
Kosrae17.75"14.64"14.91"14.22"14.22"10.94"13.83"16.11"16.67"12.93"16.06"17.51"213.87"
Kwajalein6.72"6.93"9.87"9.74"10.74"11.18"11.28"6.66"3.16"2.64"2.35"5.26"90.41"
Lukonor11.69"11.65"15.93"14.04"10.15"11.32"9.08"11.27"8.41"8.93"9.26"11.31"151.36"
Majuro10.11"11.01"11.17"11.69"11.17"12.73"13.44"11.39"7.74"6.88"6.58"9.42"125.25"
Pago Pago9.66"5.33"5.55"5.38"6.53"9.26"10.14"12.84"13.34"12.00"10.68"9.39"125.57"
Pohnpei19.96"14.81"15.43"14.26"12.55"15.27"14.83"16.08"13.18"9.55"13.17"18.41"182.36"
Saipan2.38"3.62"8.91"13.13"10.09"10.62"5.61"3.85"2.53"2.59"1.89"2.63"70.25"
Yap7.85"12.04"15.08"14.82"13.50"12.18"8.83"8.51"6.39"5.19"4.56"5.63"120.31"

As measured by percent of normal precipitation, Lukunor was drier than normal in the short term (April, the last 3 months [February-April], and the year-to-date [January-April]) and long term (last 12 months [May 2022-April 2023]). Kapingamarangi was drier than normal at the 3- and 12-month time scales, but wetter than normal for April and year to date. Airai was drier than normal for April but near to wetter than normal at the other 3 time scales. Pago Pago was barely drier than normal in the long-term but near to wetter than normal in the short-term. Chuuk, Guam, Kosrae, Kwajalein, Majuro, Pohnpei, Saipan, 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 during April and the last 2 to 24 months was generally above normal across the main islands. Longer time periods had a mixed anomaly pattern (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 2 months were drier than normal in the southern islands, while drier-than-normal conditions at some western islands were evident at 3 to 6 months and 48 months, and persistent dryness was apparent at all time scales in the southwest (Jaluit) (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 April 30 USDM produced for the USAPI, abnormal dryness continued at Jaluit, began at Ulithi, and ended at Kapingamarangi; moderate drought ended at Kwajalein; and severe drought improved to abnormal dryness at Wotje. The rest of the USAPI stations were free of drought and abnormal dryness.

The National Weather Service (NWS) office in Guam issued two Drought Information Statements (DGT) for drought in April (on April 11 and 27). The first noted that several islands in the northern RMI (north of 9 degrees N latitude) requested drought assistance in the last few weeks, with low water catchment levels, browning of vegetation, and brackish well water reported. The second noted that widespread rains recently returned to the northern RMI, improving water supplies, but lingering drought conditions persisted, so residents across the northern islands were still encouraged to conserve water as there may be dry stretches the next few weeks. Reports from Palau indicated that below-normal rainfall in April resulted in a drop in the reservoir level, but early May rains replenished the dam. In late April, Ulithi catchments were reported to be a little over 50% full and some vegetation was browning.

Satellite observations of vegetation health (VHI, stressed vegetation, drought stress) on Guam generally indicated no drought concerns.

April 2023 precipitation ranks were mostly on the median to wet side of the historical distribution, based on data available at the time of this report. Record to near-record dryness was still occurring at Kapingamarangi and Lukunor at longer time scales:

  • Kapingamarangi: 4th wettest April (in a 31-year record), but 2nd driest rank for May-April and 3rd driest rank for June-April.
  • Lukunor: 12th driest April (39 years), and driest July-April through May-April.
  • Jaluit: 15th driest April (40 years) and 6th driest August-April and May-April.
  • Ulithi: 14th driest April (41 years) and 8th driest June-April.

At the wet end of the scale, Mili had the wettest rank for October-April through June-April, and Woleai had the wettest rank for May-April.

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 April 2023, November 2022-April 2023 (last 6 months), and May 2022-April 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.

April 2023 USAPI Precipitation Ranks (1 = driest)
StationApril 2023Nov 2022-Apr 2023May 2022-Apr 2023Period of Record
RankYearsRankYearsRankYears
Ailinglaplap3840323835371981-2023
Airai1672517261701951-2023
Chuuk5872567242711951-2023
Fananu57--6--22003-2023
Guam5067626645661957-2023
Jaluit154010386371981-2023
Kapingamarangi283111262181962-2023
Kosrae3053224327361954-2023
Kwajalein5171377152711952-2023
Lukunor12396381261981-2023
Majuro5269516942681954-2023
Mili2139353633341981-2023
Nukuoro3140343832371981-2023
Pago Pago4358305728571966-2023
Pingelap3539--35--331981-2023
Pohnpei6472497268711951-2023
Saipan4043333430341981-2023
Ulithi1441203710361981-2023
Utirik--19--8--41985-2020
Woleai3944293426261968-2023
Wotje3540323728361981-2023
Yap3972357240711951-2023
Map of USAPIApril 2023 Precipitation (Inches)
Map of USAPI April 2023 Percent of Normal Precipitation
Map of USAPI February 2023-April 2023 Percent of Normal Precipitation
Map of USAPI January-April 2023 Percent of Normal Precipitation
Map of USAPI May 2022-April 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 in April were variable across the Southeast, while precipitation was above average across most of the region. The driest locations were found across northern Virginia, southern portions of Alabama, Georgia, and South Carolina, and most of Florida's Nature Coast, where monthly totals were as much as 3 inches (76.2 mm) below average (less than 75 percent of normal). Precipitation was variable across Puerto Rico, with mostly above average amounts in the eastern half of the island and below average amounts in the western half. For the second consecutive year, San Juan, PR recorded at least a trace of precipitation on every day in April. These are the only two such occurrences on record (since 1898). Precipitation was below average across the U.S. Virgin Islands.

Cool and wet weather in April resulted in an elimination of abnormally dry (D0) conditions across parts of southern Alabama, southwest Georgia, and the western Panhandle of Florida, as well as much of the Carolinas and southern Virginia. Improvements of at least one drought category were also noted across South Florida. Moderate (D1) drought was eliminated across the eastern half of Puerto Rico but persisted across the northwest and southern slopes. Drought also persisted across the Virgin Islands, with abnormally dry (D0) conditions on Saint John, moderate (D1) drought on Saint Thomas, and severe (D2) drought on Saint Croix. Moderate (D1) drought expanded across northeast Florida and much of Virginia, and was introduced in the District of Columbia for the first time since October 2019. Severe (D2) drought persisted across much of the Florida Peninsula, with a band of extreme (D3) drought emerging from the Tampa Bay area up along the Nature Coast. Burn bans and water restrictions were noted across several counties. Overall, about 15 percent of the region was in abnormally dry (D0) conditions by the end of the month (down by about 20 percent from March), while moderate (D1) to extreme (D3) drought covered about 19 percent of the region (up by about 3 percent from March).

In Florida, severe drought covered much of the citrus region, though beneficial rain did occur towards the end of the month. Pastures were in mostly poor to fair condition resulting in an increase in supplemental feed for cattle. Irrigation was being run across much of the state, while peanut and cotton planting progressed well throughout the month. Continued warm, dry, and windy weather resulted in low water levels across the Caribbean, with reports of dried-up farm ponds in parts of Puerto Rico. Egg production in the U.S. Virgin Islands has decreased by 50 percent due to the hot and dry conditions. Many farmers on the islands are moving to more drought-tolerant crops and those that grow quickly to help maximize production.

South

As explained by the Southern Regional Climate Center, temperatures were near to slightly below normal for much of the Southern region for the month of April, while precipitation was below normal for the western and northern portions of the region and well above normal along the Gulf Coast in Texas and Louisiana, much of eastern Texas, southern Arkansas, and northwestern Louisiana.

During April, the spatial extent of drought conditions remained relatively stable across the Southern region, with improvements largely limited to eastern and deep south Texas. The percentage of the region experiencing moderate drought (D1) or worse decreased from 41.88 percent on April 4 to 34.98 percent on May 2. As of May 2, much of central and western Texas, the Texas Panhandle, and western Oklahoma remained in drought conditions, with much of it being extreme (D3) or exceptional (D4). Moderate drought conditions persisted along the southeast Louisiana coast. Degradation was common in the Texas Panhandle and western Oklahoma during April. In the areas experiencing drought, the primary impacts are low reservoir levels, low streamflow, and poor conditions of pasture and crops. As of April 30, 61 percent of the winter wheat in Oklahoma and 57 percent of winter wheat in Texas was rated as Poor to Very Poor condition. Higher water levels and flows in areas north of the region have contributed to improvements in water levels at gauges along the lower Mississippi River, though levels remained below their historical mean levels for this time of year.

Midwest

As described by the Midwest Regional Climate Center, the average April temperature for the Midwest was 48.4 degrees F (9.1 degrees C), which was 0.3 degrees F (0.2 degrees C) below the 1991-2020 normal. April precipitation totaled 3.16 inches (80 mm) for the Midwest, which was 0.51 inch (13 mm) below normal, or 86 percent of normal. Across the region, monthly precipitation anomalies were below normal in the lower Midwest and well above normal in the upper Midwest.

Just over 80 percent of the Midwest was free of drought or dryness during April, mostly east of the Mississippi River. In the west, drought and dryness persisted or expanded. Iowa continued to be the epicenter of drought in the region, with about 30 percent of the state affected by moderate (D1) to exceptional (D4) drought and about 30 percent listed as abnormally dry. Conditions worsened in Missouri, with about 11 percent of the state in drought by month's end, up 9 percent from last month. In Minnesota, dryness lingered in about 40 percent of the state while D1 affected just over 1 percent.

Northeast

As summarized by the Northeast Regional Climate Center, a warm April started with intensifying dryness but ended with a deluge. The Northeast had its fifth warmest April since records began in 1895 and received 3.55 inches of precipitation, 95 percent of normal. The USDM from April 4 showed 2 percent of the Northeast in moderate drought and 9 percent as abnormally dry. During April, portions of the Mid-Atlantic, southeastern New York, and southern New England saw increasing precipitation deficits, below-normal streamflow, and reduced soil moisture. This led to the expansion of moderate drought and abnormal dryness across these areas. The USDM from April 25 showed 6 percent of the Northeast in moderate drought and 22 percent as abnormally dry. In addition, there was an increased risk of wildfires, with West Virginia issuing a week-long ban on all outdoor burning. The dry conditions also likely played a role in fueling a wildfire in Baltimore County, Maryland, that consumed 700 acres, the county's largest fire event since the 1970s, as well as a few large wildfires in New Jersey.

High Plains

As summarized by the High Plains Regional Climate Center, northern parts of the High Plains continued to deal with brutal winter conditions, while the southern portions were dry once again. Both parts of the region were dealing with issues related to their ends of the extremes. Cooler temperatures dominated and snow continued to pile up in the Dakotas and Wyoming, with numerous impacts. In the southern Plains, drought-related issues continued to plague the population. Several significant wildfires broke out in Nebraska due to the dry conditions. The state has implemented a burn ban to help reduce the number of fires. Kansas agricultural producers are preparing for another year of drought, with farmers scrambling to find food sources for their already culled herds.

April precipitation was below normal for much of the region, with Nebraska very dry. The majority of the state was below 25 percent of their normal precipitation, leading to multiple locations ranking in the top 10 driest. Southwestern Kansas finally received some meaningful precipitation; however, it was not nearly enough to help improve the dire drought situation. North Platte, Nebraska was arguably the driest location in the region, with only 0.04 inch (1.02 mm) of precipitation. This tied with 1928 for the driest April on record. Nearby Grand Island only observed 0.15 inch (3.81 mm), ranking 3rd driest. Other locations in the state ranking in the top 10 driest include Chadron, Lincoln, and Norfolk.

For the second month in a row, drought conditions improved in the Dakotas while worsening in the southern Plains. Central Kansas and the front range of Colorado experienced up to a three-class degradation in April alone. Overall, there was a 6 percent decrease in D0 to D4 (abnormally dry to exceptional drought conditions). Rapid snowmelt after well-above-normal temperatures caused North Dakota to observe a 40 percent decrease in D0 to D4. Soil moisture greatly improved, while some minor flooding is taking place in the state. While some beneficial precipitation occurred in southwestern Kansas late in the month, the majority of the state has experienced a poor spring for precipitation. The central part of the state observed a multi-class degradation, with a 10 percent increase in D4. Elsewhere in the region, other localized improvements and worsening were observed.

West

As summarized by the Western Regional Climate Center, much of the western U.S. experienced near-to-below normal temperatures during April. Aside from western Oregon and Washington, the western U.S was drier than normal during April. The colder- and drier-than-normal conditions persisted across the western U.S. during April 2023 as weak high pressure persisted offshore driving the stormtrack northwards. This brought a generally dry and zonal flow to the western states and the welcome precipitation to coastal Oregon and Washington. Many locations with long-term observations in central and southern California, the southern half of Nevada and throughout Arizona and New Mexico recorded a record dry April. Zero precipitation was commonly observed in these places. Snowmelt began in earnest throughout much of the western U.S. with the dry and sunny conditions. The coldest temperatures occurred in southwestern Wyoming, far northwestern Utah, and southeastern Idaho. Colder-than-normal conditions in Alaska limited melt rates of the record snowpack. Temperatures and precipitation in Hawaii were near-normal to above normal.

Snowpack conditions at the end of April remains well above normal (more than 150 percent of normal) across the southern tier of the western U.S. and the western Cascades in the northern tier. Further inland in the northern tier, near- to slightly-below-normal conditions are found. Sunny conditions and several warm spells with high daytime temperatures and above-freezing nighttime temperatures spurred rapid snowmelt in Utah, California and Nevada. Melt out has occurred in the lower elevation areas of Arizona and New Mexico; however, high elevations continue to maintain an impressive snowpack. The lowest snowpacks (less than 50% of normal) are found in northwestern Montana and northwestern Wyoming. Maritime and intermountain snowpacks have achieved the ready-to-melt "ripe" state (approximately 50% density) while some higher elevation continental snowpacks, which typically ripen during May, remain at lower densities (30-40%).

While all western states still have some level of drought, the cool, wet, and snowy winter of water year 2023 led to dramatic short-term drought improvements in many locations. Compared to the start of the water year when less than 4% of the West had no drought, as of May 2, 46% of the West is drought free. The remaining areas of extreme to exceptional drought, accounting for less than 1.25% of the West, are found in far northeastern New Mexico, southeastern Wyoming, and central Oregon.

April 2023 brought near-normal to above-normal precipitation and both warmer-than-normal and close-to-normal temperatures to Hawaii. Drought conditions are limited to the far northern coast of the Island of Hawaii where a small area of moderate drought exists. April brought historic cold to the northern two-thirds of Alaska, limiting melting of the record snowpack built throughout a wet and snowy winter. With zero measured precipitation, Tanana tied its driest April on record (0.3 inches below normal). With 0.91 inch of precipitation, Gulcana observed its 2nd wettest April in 83 years of records (0.7 inch above normal). Cold conditions limited sea ice melt over the northern Bering Sea region. Sea ice extent was typical of the 1991-2020 median.

Additional Resources


Citing This Report

NOAA National Centers for Environmental Information, Monthly Drought Report for April 2023, published online May 2023, retrieved on July 24, 2024 from https://www.ncei.noaa.gov/access/monitoring/monthly-report/drought/202304.