Issued 14 June 2022
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
- Based on the Palmer Drought Index, severe to extreme drought affected about 32% of the contiguous United States as of the end of May 2022, a decrease of about -1% from last month. About 4% of the contiguous U.S. fell in the severely to extremely wet categories.
- About 43% of the contiguous U.S. fell in the moderate to extreme drought categories (based on the Palmer Drought Index) at the end of May
- On a broad scale, the 1980s and 1990s were characterized by unusual wetness with short periods of extensive droughts, the 1930s and 1950s were characterized by prolonged periods of extensive droughts with little wetness, and the first two decades of the 2000s saw extensive drought and extensive wetness (moderate to extreme drought graphic, severe to extreme drought graphic).
- 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".
According to the weekly U.S. Drought Monitor (USDM), as of May 31, 2022, 49.3% of the contiguous U.S. (CONUS) (41.42% of the U.S. including Alaska, Hawaii, and Puerto Rico) was classified as experiencing moderate to exceptional (D1-D4) drought.
Detailed Drought Overview
The upper-level circulation during May 2022 was very active with several shortwave troughs and closed lows moving through a strong westerly jet stream flow. The troughs frequently lingered over the western CONUS, especially the Pacific Northwest, before moving eastward. This resulted in an anomalous long-wave trough pattern in the monthly mean flow over the northwestern CONUS and southwestern Canada, which was associated with cooler-than-normal monthly temperatures over the northwestern quarter of the CONUS. The short-wave troughs and closed lows moved across the eastern U.S. throughout the month, but they moved through a long-wave ridge over the eastern CONUS which was evident in the monthly upper-level circulation pattern. Warmer-than-normal monthly temperatures over the eastern CONUS were associated with the ridging. At times the eastern ridge extended westward into the southern Plains, while at other times during the month a ridge over the Southwest extended eastward into the southern Plains. The result was a period of unusually warm temperatures over New Mexico and especially Texas. Both Abilene and San Angelo, Texas, reported a record number of days in May 2022 with the maximum temperature 100 degrees F or higher. The migrating troughs and closed lows and their associated surface lows and fronts brought above-normal precipitation to parts of the Pacific Northwest, northern Rockies, and northern Plains to Upper Mississippi Valley. They also tapped Gulf of Mexico moisture to spread above-normal precipitation over parts of the central Plains, Gulf of Mexico Coast, Ohio Valley, and Appalachians to Mid-Atlantic coast. Precipitation in the east was enhanced when an upper-level low over the Atlantic Ocean retrograded and moved westward over the southeastern CONUS at mid-month. The effects of a continuing La Niña and upper-level ridging kept the Southwest to southern Plains drier than normal for the month with widespread record dryness, the eastern ridge helped keep the Northeast and parts of the Southeast to Mid-Mississippi Valley drier than normal, while drier-than-normal weather dominated much of the western High Plains and parts of the Great Lakes.
With above-normal precipitation falling over many drought areas, drought or abnormal dryness contracted or was reduced in intensity in parts of the Pacific Northwest, northern Rockies, Great Plains, Mississippi Valley, Gulf of Mexico coast, northern New England, Mid-Atlantic states, and Southeast, as well as Hawaii. Those areas missing this month's beneficial rains saw expansion or intensification of drought or abnormal dryness and included the Southwest to parts of the southern and central Plains, plus other parts of the Tennessee and Ohio valleys, the coastal Carolinas, and southern New England, as well as Puerto Rico and Alaska. Drought contraction exceeded expansion with the USDM-based national moderate-to-exceptional drought footprint across the CONUS decreasing from 53.8 percent at the end of April to 49.3 percent at the end of May (from 45.0 percent to 41.4 percent for the 50 States and Puerto Rico). But the most intense categories of drought (extreme to exceptional) increased in area from 18.5 percent to 20.1 percent for the CONUS (from 15.5 percent to 16.8 percent for the 50 States and Puerto Rico). According to USDM statistics, 40 percent or more of the CONUS has been in moderate drought or worse for the last 89 weeks. This is a record in the 22-year USDM history. The previous record was 68 consecutive weeks (June 19, 2012 to October 1, 2013).
According to the Palmer Drought Index, which goes back to the beginning of the 20th century, about 42.1 percent of the CONUS was in moderate to extreme drought at the end of May, which is less than the end of April. The percent area of the CONUS in moderate to extreme drought has hovered between roughly 35 and 53 percent for the last 21 months (since September 2020).
Numerous reports of drought impacts were received during May by the National Drought Mitigation Center. The impacts of the drought can be seen in several drought indicators, especially in the West, Plains, and Atlantic Coast. These include:
- dry soils (VIC, CPC [anomaly, percentile], NLDAS, and Leaky Bucket models; and GRACE surface and root zone, crop CASMA topsoil and subsoil anomaly, crop CASMA topsoil and subsoil categorical, SPoRT surface and deeper layer, and USDA observations);
- low ground water (GRACE, USGS) and springwater levels;
- some low streamflow levels (USGS station and huc maps);
- high evapotranspiration (ESI) (1-, 2-, and 3-month EDDI);
- poor vegetation (VegDRI, VCI, NESDIS satellite-based VHI and stressed vegetation); and
- the Quick Drought Response Index (QuickDRI).
- Many reservoir levels were low and falling in western Texas and much of the West (California; Washington; Oregon map 1, 2, 3, 4, 5; Idaho map 1, 2, 3; Southwest map 1, 2, 3, 4, 5, 6, 7, 8, 9; westwide station percentile and station and basin percent of average map), with many at or near record low levels.
- Large wildfires burned throughout the month in the Southwest and southern Plains, and developed at times in parts of the East, Far West, central Plains, Great Lakes, and Gulf of Mexico coast (wildfire maps for May 1, 4, 12, 16, 17, 20, 23, 28, 31). As of May 31, over 27,000 fires had burned over 1.8 million acres nationwide; the number of fires is about 6,000 more than the ten-year average for this time of year, and the acreage burned is more than twice the ten-year average.
Drought conditions at the end of May, as depicted on the May 31, 2022 USDM map, included the following core drought and abnormally dry areas:
- Moderate (D1) to severe (D2) drought extended from the West Coast to Rocky Mountains and into the adjacent Great Plains, with a large areas of extreme (D3) and exceptional (D4) drought. May precipitation was above normal across much of the Pacific Northwest and parts of the northern Rockies, but below normal across the southern half of the West and in parts of Montana and Wyoming, with large parts of the Southwest (from southern California to New Mexcico) experiencing a record dry May (low-elevation precipitation anomaly map for May; high-elevation SNOTEL station and basin precipitation anomaly maps for May; high-elevation SNOTEL station precipitation percentile map for May). In spite of the May precipitation, much of the West continued to be drier than normal at longer time scales (low-elevation precipitation anomaly maps for last 2, 3, 4, 5, 6, 8, 9, 11, 12 months; high-elevation SNOTEL station and basin precipitation anomaly maps for last 5, 12 months; high-elevation SNOTEL station precipitation percentile maps for last 5, 12 months). Westwide, May 2022 ranked as the 92nd driest (37th wettest) May in the 128-year record, but January-May 2022 still ranked as the fifth driest January-May and June 2021-May 2022 ranked as the 32nd driest such 12-month period. But when June 2021-May 2022 is combined with June 2020-May 2021, June 2020-May 2022 ranked as the second driest such 24-month period, behind June 2019-May 2021. The percent area of the West experiencing moderate to exceptional drought, according to USDM statistics, decreased from 91.3 percent at the end of April to 86.8 percent at the end of May. The percent area of the West (from the Rockies to the West Coast) in moderate to extreme drought (based on the Palmer Drought Index) fell for a second month, dropping to 70.8 percent at the end of May 2022.
- Moderate to exceptional drought continued in the Great Plains, especially in the southern portions, with drought contraction occurring in many areas while expansion or intensification occurred in fewer areas. In the central to northern Plains, the moderate to exceptional drought area decreased from 75.1 percent at the end of April to 65.5 percent at the end of May. In the southern Plains, the moderate to exceptional drought area shrank from 79.3 percent at the end of April to 73.8 percent at the end of May. In the Lower Mississippi Valley, moderate to extreme drought fell slightly from 22.9 percent at the end of April to 20.3 percent at the end of May. Taken together, the southern Plains, Lower Mississippi Valley, and Tennessee (South Region) saw moderate to exceptional drought decrease from 53.7 percent at the end of April to 49.3 percent at the end of May.
- Moderate to severe drought lingered in western Iowa, with the drought area in the Midwest continuing to shrink — from 1.5 percent at the end of April to 0.8 percent at the end of May.
- In the Northeast, moderate drought continued in northern Maine and developed in southern New England, with the regional drought area increasing from 1.4 percent at the end of April to 2.7 percent at the end of May.
- In the Southeast, the total moderate to severe drought area shrank from 16.1 percent at the end of April to 10.3 percent at the end of May, but the severe drought area increased from 2.6 percent to 3.1 percent.
- A small area of exceptional drought developed in Hawaii, but the total drought area contracted from 47.1 percent at the end of April to 40.4 percent at the end of May.
- In the Caribbean, moderate drought increased from 3.4 percent of Puerto Rico at the end of April to 17.9 percent at the end of May, while in the U.S. Virgin Islands (USVI), severe drought worsened to extreme drought on St. Croix, and moderate drought returned to St. John and St. Thomas.
In the U.S.-Affiliated Pacific Islands (USAPI), compared to last month:
- severe drought improved to moderate drought at Wotje in the Marshall Islands;
- moderate drought redeveloped at Kapingamarangi (Federated States of Micronesia); and
- abnormal dryness returned to the Marianas.
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.
Used together, the Palmer Z Index and PHDI maps show that short-term drought occurred across much of the Southwest to southern and central Plains (from southern California to Texas, western Kansas, and southwestern Nebraska), expanding or intensifying long-term drought (PHDI maps for May compared to April), and in much of the Northeast and parts of the Great Lakes, shrinking long-term wet conditions. Short-term wet conditions occurred over the Pacific Northwest, northern Rockies, and central to eastern Kansas, decreasing long-term drought, and in the northern Plains to Upper Mississippi Valley, increasing 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.
The SPI maps illustrate how moisture conditions have varied considerably through time and space over the last two years. Dryness covered southern parts of the West at all time scales and northern parts at the 6-, 12-, and especially 24-month time scales. North central parts of Montana were dry at all time scales. Much of the southern and central Plains was dry at 3 to 12 months, the western parts were dry at 2 and 24 months, and southern Texas was dry at 1 to 2 months. The dryness extended along the Gulf of Mexico coast and Lower Mississippi Valley at 6 to 12 months, and across Nebraska into Iowa at 24 months. Dryness was evident in parts of southern Wisconsin and northern Illinois at 9 to 24 months. Parts of New England were dry at 1 month, southern parts were dry at 1 to 6 months, and northern parts were dry at 24 months. Parts of the Mid-Atlantic to Southeast coat were dry at 1 to 12 months, especially the Carolina coast at 9 months. Wet conditions dominate the northern Plains at 1 to 12 months, the Pacific Northwest at 1 to 3 months, coastal Washington at all time scales, eastern Kansas and northeast Oklahoma to the Mid-Mississippi Valley at 1 to 3 months, parts of the central to eastern Gulf of Mexico coast at 1 to 3 months and 12 to 24 months, the southern Appalachians and Ohio Valley to Pennsylvania and New Jersey at 1 and 2 months, much of the Great Lakes at 2 to 24 months, and parts of the Northeast at 2 to 24 months. An interesting pattern continues at the 24-month time scale — very dry conditions dominate across the West to western portions of the Plains, while very wet conditions dominate the Lower Mississippi Valley to Great Lakes and eastward.
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, May marks the end of climatological spring, which is the transition season from the time of year when evapotranspiration is minimal to when it is maximum. During May 2022, temperatures were much above normal in the southern tier and East Coast states, especially New Mexico and Texas, and much below normal in the Northwest. The southern Plains were warmer than normal for the last 2 months, but near- to cooler-than-normal temperatures dominated much of the CONUS for the last 3 to 5 months, except for some coastal areas. This temperature anomaly pattern resulted in more severe SPEI values than SPI values in the South and Southwest for May (SPEI map vs. SPI map) and April-May (SPEI map vs. SPI map), but similar patterns of anomalies of similar magnitude for the last 3 to 5 months (SPEI maps for last 3, 4, 5 months) (SPI maps for last 3, 4, 5 months). At longer time scales, warmer-than-normal temperatures dominated, first in the South then more broadly across the CONUS. This contributed to more severe SPEI values than SPI values for the last 6 to 12 months (SPEI maps for last 6, 9, 12 months) (SPI maps for last 6, 9, 12 months).
Much of the West was extremely warm during 2021 and earlier years. This increased evapotranspiration and resulted in more extreme SPEI values than SPI values at the 1- to 6-year time scales (SPEI maps for last 12, 18, 24, 36, 48, 60, 72 months) (SPI maps for last 12, 18, 24, 36, 48, 60, 72 months).
May 2022 was wetter than normal across parts of the Hawaiian Islands, especially the Big Island, and drier than normal across other parts. The last 2 to 5 months had a progressively drier-than-normal character, with dryness centered over Oahu and Molokai at 2 months and spreading across the main islands by 5 months. A wet December 2021 resulted in a mixed precipitation anomaly pattern at the 6-month time scale. At 8 to 12 months, there were still wetter-than-normal areas on the Big Island and Oahu, but drier-than-normal conditions dominated on Maui, Molokai, and Kauai. At longer time scales, a mixed anomaly pattern was evident with wetter-than-normal conditions dominating the further out in time (last 1, 2, 3, 4, 5, 6, 8, 9, 11, 12, 24, 36, 48, 60 months) (climate engine model percent of normal precipitation map for the last month). Monthly streamflow was mostly near normal except for some below-normal streams on Oahu. Vegetation was stressed on parts of all of the main islands, but especially on Molokai, Maui, and the Big Island (satellite analyses of stressed vegetation, drought risk, VHI). Drought or abnormal dryness expanded on Molokai and Maui but contracted on the other islands. The overall drought footprint shrank from 47.1 percent last month to 40.4 percent on the May 31st USDM map.
May 2022, April-May 2022, and March-May 2022 were drier than normal across most of Alaska. The dryness was especially severe in the southwest and south coastal areas, with parts of the Aleutians having the driest May on record. At the 4- to 5-month time scales, northern portions of the state were drier than normal and southern portions wetter than normal, except for parts of the Northwest Gulf and Cook Inlet climate divisions which were drier than normal. By 6 months, most of the state was wetter than normal; drier-than-normal conditions lingered in the Aleutians to coastal Northwest Gulf and a few locations along the North Slope. This pattern continued to longer time scales (low elevation station precipitation anomaly maps for the last 1, 2, 3, 4, 5, 6, 8, 9, 11, 12, 24, 36, 48, 60 months) (high elevation SNOTEL station precipitation percentile map for the last 1, 2, 3, 5, and 12 months) (high elevation SNOTEL station precipitation anomaly maps for May 2022 and October 2021-May 2022) (SNOTEL basin precipitation anomaly map for October 2021-May 2022) (SNOTEL basin and station precipitation anomaly maps for the last 1, 2, 3, 5, and 12 months) (climate division precipitation rank maps for the last 1, 3, 5, 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 warmer than normal in northern and southern parts of the state and near to cooler than normal in central portions and in the southern panhandle. Warmer-than-normal temperatures expanded across the western portions of Alaska by the 3-month time scale and were replaced by near- to cooler-than-normal temperatures in the north by 4 months. At the 5- to 6-month time scales, the warmer-than-normal area was confined to the southwestern third of the state. By 12 months, near to cooler-than-normal temperatures had spread to more of the state (low elevation station temperature anomaly maps for the last 1, 2, 3, 4, 5, 8, 12 months) (climate division temperature rank maps for the last 1, 3, 5, 6, and 12 months) (gridded temperature percentile maps for the last 1, 3, and 5 months) (Leaky Bucket model temperature percentile map). End-of-May observations of snowpack and snow water equivalent (SWE) indicated that snow had melted out of many low elevation locations, especially in the southern areas, but abundant high elevation snowpack continued (satellite-based SWE; SNOTEL station [1, 2] and basin SWE; SNOTEL snowpack amount). Modeled soil moisture and experimental satellite-based observations of soil moisture (GRACE root zone and surface soil moisture; SPoRT relative percent of soil moisture for 0-10 cm [0-4 inches] depth, 10-40 cm [4-16 inches] depth, 40-100 cm [16-39 inches] depth, 100-200 cm [39-79 inches] depth) and groundwater showed drier-than-normal conditions in some areas, especially southern and southwestern areas and in upper soil layers. Monthly streamflow (for those streams that were not frozen) was mostly near to above normal with some below-normal streams in the panhandle.
The month began with a large wildfire (the Kwethluk Fire) burning in the tundra of the Yukon Delta National Wildlife Refuge in southwest Alaska, but it diminished early in the month (wildfire maps for May 1 and 4). The Alaska Center for Climate Assessment and Policy noted that precipitation deficits, since the winter snowpack meltout was complete, were coupled with unusually warm weather in the southwest and especially in the northwest Kenai Peninsula, across urban Anchorage, to the lower Susitna River valley, and in the lower Matanuska Valley, which is an area that has significant agricultural activity. Impacts noted include an increased wildfire threat and possibly some need for watering of gardens; river levels were mostly high, fed by higher elevation snowmelt. Satellite observations of vegetative health showed stressed vegetation due to moisture stress and thermal stress.
Abnormal dryness expanded in southern portions of the state and an area of moderate drought was introduced in the Cook Inlet region, as seen on the May 31st USDM map. The moderate drought area was about 1 percent of the state, but the area of abnormal dryness expanded to about 16 percent of Alaska.
Puerto Rico and U.S. Virgin Islands
May 2022 was drier than normal across Puerto Rico (PR) and the U.S. Virgin Islands (USVI). Dry conditions extended across much of the region at the 2- and 3-month time scales. A wet February resulted in above-normal precipitation at the 4- to 6-month time scales, but several dry areas persisted. The USVI and much of PR were drier than normal at longer time scales (radar-based precipitation anomaly estimates for the last 1, 2, 3, 5, 6, 8, 12 months) (low elevation station precipitation maps for the last 1, 2, 3, 4, 5, 6, 8, 9, 11, 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 dry along the southern and northern coasts and some eastern interior regions of PR (root zone soil saturation fraction; 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 show areas of vegetative stress (VHI, drought risk, stressed vegetation). Monthly streamflow was below normal at many locations in PR, with some record low gauges. In the USVI, groundwater during May continued to decline on St. Thomas, St. John, and St. Croix. The groundwater level on St. Croix in May 2022 reached a new record low value compared to the 2016-2022 record. The May values at St. John and St. Thomas were very low but had not reached record low values based on the 2016-2022 period, although the St. John value was the lowest since November 2016 and the St. Thomas value was the lowest in the last 12 months. Moderate drought expanded from 3.4 percent of PR at the end of April to 17.9 percent at the end of May, while in the USVI, severe drought worsened to extreme drought on St. Croix, and moderate drought returned to St. John and St. Thomas.
CONUS State Precipitation Ranks
May 2022 was drier than normal across the Southwest to southern Plains and western portions of the central and northern Plains, and in parts of the Midwest, Southeast, and Northeast. Record-dry conditions occurred locally across much of the Southwest. Ten states had a precipitation rank in the driest third of the 128-year historical record for May, including one in the top ten driest category — Arizona (fifth driest).
Spring (March-May) 2022 was drier than normal across the Southwest to southern and central Plains, much of Montana, and in parts of the Tennessee and Ohio Valleys and Atlantic coast. Ten states had a precipitation rank in the driest third of the historical record for March-May, including two in the top ten driest category — New Mexico (sixth driest) and Arizona (tenth driest).
The year to date (January-May 2022) was drier than normal in much the same areas as spring — across the Southwest to southern and central Plains, much of Montana, and parts of the Atlantic coast, with record dry conditions occurring locally from California to Texas. Eleven states had a precipitation rank in the driest third of the historical record for January-May, including six in the top ten driest category — California (driest on record); Arizona, Nevada, and Utah (each third driest); New Mexico (seventh driest); and Texas (eighth driest).
The last six months (December 2021-May 2022) were drier than normal in much the same areas as the year to date — across the Southwest to southern and central Plains, much of Montana, parts of the Pacific Northwest, parts of the Mississippi Valley, and more of the Atlantic coast. Fifteen states had a precipitation rank in the driest third of the historical record for December-May, including three in the top ten driest category — Texas (sixth driest), New Mexico (ninth driest), and California (tenth driest).
The last 12 months (June 2021-May 2022) were drier than normal across most of the West and Great Plains, parts of the Mississippi Valley, the Mid-Atlantic coast, and northern New England, with locally record dry conditions in northeast Colorado. Eleven states had a precipitation rank in the driest third of the historical record for June-May, including one in the top ten driest category — Montana (ninth driest).
During May 2022, the Primary Corn and Soybean agricultural belt was mostly near to warmer than average with a some areas very dry and other areas very wet. The month ranked as the 42nd wettest and 30th warmest May, regionwide, in the 1895-2022 record.
March marks the beginning of the growing season for the Primary Corn and Soybean belt. March-May 2022 was mostly near to cooler than normal with a mixed precipitation anomaly pattern. The period ranked as the 50th warmest and 39th wettest March-May, regionwide, on record.
According to the U.S. Department of Agriculture (USDA), as of May 31, 2022, drought affected approximately 83 percent of sorghum production, 66 percent of barley production, 59 percent of the sheep inventory, 54 percent of winter wheat production, 51 percent of cotton production, 51 percent of the cattle inventory, 43 percent of the milk cow inventory, 37 percent of rice production, 36 percent of hay acreage, 25 percent of spring wheat production, 19 percent of corn production, and 10 percent of soybean production. All of these statistics are less than they were a month ago. Based on May 29 USDA statistics, 40 percent of the nation's winter wheat and 46 percent of the nation's pasture and rangeland were in poor to very poor condition, and 25 percent of the topsoil and 30 percent of the subsoil were short or very short of moisture (dry or very dry). The table below lists those states having 30 percent or more of topsoil or subsoil moisture short or very short, or 30 percent or more of the pasture and rangeland or winter wheat in poor or very poor 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, American Samoa, basinwide), May 2022 was drier-than-normal in the Marianas, the southern parts of the FSM, southeast RMI, and in American Samoa. It was near to wetter than normal across Palau and most of the RMI and FSM.
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) in the Marianas and parts of the FSM and RMI. May 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 May 2022, which is in the dry season for most locations in northern and eastern Micronesia. Precipitation was below the monthly minimum but above normal (1981-2010 normal), because the normals are low, at:
- Wotje: May 2022 precipitation 6.85 inches, May normal mean 4.92 inches
At some stations, the dry season is not as pronounced or, for Pago Pago and Lukunor, this is the wet season, so the normal monthly precipitation is above the monthly minimum. Precipitation was above the monthly minimum but below normal at:
- Lukunor: May 2022 precipitation 10.27 inches, May normal mean 12.78 inches, May normal median 11.69 inches
- Jaluit: May 2022 precipitation 8.42 inches, May normal mean 10.85 inches
- Pago Pago: May 2022 precipitation 9.32 inches, May normal mean 10.62 inches, May normal median 9.66 inches
In the table below, the station identified as Koror is Palau International Airport (Airai).
As measured by percent of normal precipitation, Kapingamarangi was drier than normal in the short term (May, the last 3 months [March-May 2022], and the year-to-date [January-May]) and long term (last 12 months [June 2021-May 2022]). Guam was drier than normal in the short-term and near normal in the long-term. Pago Pago was near normal for May but drier than normal for the other 3 time periods. Lukunor was drier than normal at the 1- and 12-month time scales and near normal for the other 2 time scales. Saipan and Majuro were drier than normal for May but wetter than normal for the other 3 time scales. Airai, Chuuk, Kosrae, Kwajalein, Pohnpei, and Yap were wetter than normal at all 4 time scales.
Based on percent of normal average (instead of normal median values), in the Marianas Islands, precipitation during May was below normal across the islands. Wetter-than-normal conditions dominated at the 2- to 6-month time scales except over Guam, and at the 8- to 9-month time scales across the main islands. A mixed anomaly pattern was evident at 11 and 12 months, with drier-than-normal conditions dominating at the 24-month and longer time scales (percent of normal precipitation maps for the last 1, 2, 3, 4, 5, 6, 8, 9, 11, 12, 24, 36, 48, 60 months).
Based on percent of normal average (instead of normal median values), in the Marshall Islands, precipitation during May was above normal at the regular-reporting stations except Majuro and Jaluit where it was below normal. Wetter-than-normal conditions dominated for the 2- to 12-month time scales, with a mixed anomaly pattern at longer time scales (percent of normal precipitation maps for the last 1, 2, 3, 4, 5, 6, 8, 9, 12, 24, 36, 48, 60 months).
According to the May 31st USDM produced for the USAPI, severe drought improved to moderate drought at Wotje, moderate drought returned to Kapingamarangi, and abnormal dryness returned to the Marianas. 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 May (on May 6 and 20) and two in early June (on June 3 and 10) discussing the conditions in the USAPI:
- Very wet ITCZ (Inter-Tropical Convergence Zone) trade-wind weather across the central RMI continued to meander northward at times, bringing beneficial rain to Wotje and other northern islands. The observer on Wotje reported in mid May that water catchment tanks were still about 50% of capacity and vegetation was continuing to green up, but catchment levels were climbing by early June. Conditions varied quite a bit island to island but an overall wetter pattern in recent weeks led to improved conditions. Residents continued to conserve water.
- By early June, after several weeks with little to no rain, water levels for both private and public water tanks on Kapingamarangi were roughly 30% of capacity and vegetation was turning yellow. A ship recently delivered water supplies to the island. Eight 1,500 gallon water tanks were also shipped to Kapingamarangi recently. These water tanks will bolster water resources once they are installed.
The reservoir on Majuro declined slightly throughout May, ending the month with about 21.8 million gallons of water. This is below the threshold of concern for drought of 28.8 million gallons. But in this particular case, the low water level is due to one sector of the reservoir being serviced. This portion of the reservoir system typically holds 8 million gallons, so the low reservoir level is not due to drought conditions.
The dry weather in May lowered precipitation ranks at some stations, with record dryness occurring at Kapingamarangi:
- Kapingamarangi: driest May, April-May, & March-May (in a 28-year record); 2nd or 3rd or 4th driest rank for all other time periods (Feb-May thru June-May); last 12 months ranked as the 3rd driest June-May (18 years of data).
- Pago Pago: 30th driest May (57 years of data), but 5th driest March-May & Sep-May.
- Pingelap: 6th driest May (38 years).
- Saipan: 9th driest May (42 years).
- Wotje: This is a transition month, so the 6.85 inches of rain that fell in May 2022 ranked the month as the 8th wettest May in the 38-year record. The rain in recent months brought the 12-month precipitation rank to 15th driest June-May (34 years).
At the wet end of the scale, no station had the wettest May on record but several ranked wettest on record for several multi-month time periods.
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 May 2022, December 2021-May 2022 (last 6 months), and June 2021-May 2022 (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.
|Station||May 2022||Dec 2021-May 2022||Jun 2021-May 2022||Period of Record|
NOAA Regional Climate Centers
More information, provided by the NOAA Regional Climate Centers and others, can be found below.
As noted by the Southeast Regional Climate Center, temperatures were near to above average across much of the Southeast region for the month of May. Precipitation was variable across much the Southeast region for May, with only a few wet and dry extremes reported. The driest locations were found across southern Florida, northern Georgia, parts of eastern North Carolina, and Puerto Rico. Monthly precipitation totals ranged from 70 to less than 25 percent of normal across these locations. Coloso, PR (1940-2022) observed only 2.66 inches (68 mm) of precipitation, more than 7 inches (178 mm) below normal, making this the second driest May on record. In contrast, the wettest locations for the month were located across southern Alabama, the Florida Panhandle, and western North Carolina.
Drought conditions improved for parts of Virginia and Florida but intensified for parts of South Carolina, Georgia, and Puerto Rico in May. By the end of the month, only pockets of abnormally dry conditions (D0) remained in Virginia. Drought conditions stayed the same throughout the month in North Carolina, with a pocket of severe drought (D2) along the eastern North Carolina coast ringed by moderate drought (D1) and abnormally dry conditions (D0). Moderate drought (D1) ringed by abnormally dry conditions stretch from eastern South Carolina down into southern Georgia, with an embedded pocket of severe drought (D2) developing by the end of the month. In southern Florida, drought conditions improved with a pocket of moderate drought (D1) ringed by abnormally dry conditions (D0). Drought conditions slightly intensified across Puerto Rico for the month, with pockets of moderate drought (D1) ringed areas of abnormally dry conditions (D0) across the Island and pockets of moderate drought (D1) to extreme drought (D3) across the Virgin Islands.
Due to the lack of adequate rainfall across the citrus growing region of Florida, farmers had to run irrigation in all areas. Heavy rainfall eased the dry conditions in the northern part of the state and the Panhandle, which allowed producers to pick up planting peanuts and cotton after some had halted the planting due to the dryness. Moderate drought conditions in southern Georgia required farmers to run irrigation in fields. Cotton planting was halted due to a lack of soil moisture in some areas. Warm conditions with sporadic rainfall across much of South Carolina resulted in favorable planting conditions, although many producers had to run irrigation for their crops.
As explained by the Southern Regional Climate Center, precipitation was close to normal across the Southern region, averaging 3.82 inches, 0.30 inches below the 1991-2020 average, and temperatures were well above normal. The average temperature for the region was 75.2 F, 3.4 F warmer than the 1991-2020 normal and 4.0 F warmer than the 20th century average. Texas tied its second warmest May ever, at 78.0 F, 4.4 F above normal, behind only 1996, and Louisiana and Mississippi were both sixth warmest on record. Overall, the regional average temperature was fourth warmest on record, behind only 2018, 1896, and 1996. About half the state reached triple digits at least once during May. The May average temperature was the hottest on record across a large swath of Texas, from Abilene and San Angelo to Victoria and Galveston and including the major cities of Austin and San Antonio.
Drought conditions generally improved across the Southern region. As with the nation as a whole, the area in drought dropped below 50%. Severe drought coverage declined from 46% to 40%, extreme drought declined from 32% to 25%, and exceptional drought declined from 11% to 9%, despite peaking at 16% on May 17. Arkansas and Mississippi were free of drought, and Tennessee had drought appear for just one week. Louisiana showed slight improvement to 45% drought coverage and Texas showed slight improvement to 78% drought coverage. The largest change was in Oklahoma, where drought coverage decreased from 65% of the state to 43% of the state and extreme drought declined from 39% to 17%. Primary impacts continue to be agricultural (farming and ranching), but water supply impacts will intensify over the summer if drought persists.
As described by the Midwest Regional Climate Center, the May average temperature for the Midwest was 61.1 degrees F (16.2 degrees C), which was 1.4 degrees F (0.8 degrees C) above the 1991-2020 normal, and the average spring (March-May) temperature for the region was 0.5 degrees F (0.3 degrees C) below normal, with areas in the northwest up to 4 degrees F (2.2 degrees C) below normal and areas in the southeast up to 3 degrees F (1.7 degrees C) above normal. May precipitation was 4.81 inches (122 mm) for the Midwest, which was 0.43 inch (11 mm) above normal, or 110 percent of normal, and spring (March-May) precipitation totaled 11.55 inches (293 mm), which was 0.93 inch (23.6 mm) above normal.
As explained by the Northeast Regional Climate Center, the Northeast experienced a warmer-than-normal May and spring but precipitation varied. The Northeast had its 18th warmest May since records began in 1895 with an average temperature of 58.7 degrees F, 1.8 degrees F above normal. It was the Northeast's 16th warmest spring on record, with an average temperature of 47.1 degrees F, 1.3 degrees F above normal. During May, the Northeast received 3.93 inches of precipitation, 99 percent of normal. May precipitation for the 12 Northeast states ranged from 52 percent of normal in Rhode Island, its 20th driest May, to 144 percent of normal in Maryland, its 17th wettest May. Overall, seven states were on the dry side of normal. The Northeast's spring precipitation was 11.16 inches, 99 percent of normal. Seven states were drier than normal with precipitation for all 12 Northeast states ranging from 66 percent of normal in Rhode Island, its 18th driest spring, to 113 percent of normal in New Jersey.
The USDM from May 5 showed 1 percent of the Northeast in moderate drought and 17 percent as abnormally dry. Increasing precipitation deficits, declining soil moisture, and below-normal streamflow and groundwater levels led to the introduction of moderate drought in eastern Massachusetts, northern Rhode Island, and northeastern Connecticut and the introduction/expansion of abnormal dryness in coastal New England and western New York. Moderate drought and abnormal dryness persisted but contracted in western Maine. However, in southern parts of the Northeast, northern New Hampshire, and northern Vermont, plentiful precipitation allowed areas of moderate drought and abnormal dryness to ease. The USDM released on May 26 showed 2 percent of the Northeast in moderate drought and 13 percent as abnormally dry. A few Massachusetts communities implemented or enhanced water restrictions due to dry conditions. There were several brushfires in New England including a fire in New Hampshire's White Mountains that took a week to contain and consumed 250 acres.
As summarized by the High Plains Regional Climate Center, temperatures for the month of May were near-normal throughout the region, with pockets of below-normal observed in Wyoming, while precipitation for the region was mixed. Some parts of the region such as eastern Kansas were much wetter than normal, while areas such as southwest South Dakota were much drier than normal. The near-normal to cooler-than-normal temperatures were beneficial in the prevention of intensifying drought conditions. Many areas in eastern Wyoming and southwestern South Dakota observed well below-normal precipitation this month; however, the temperatures helped prevent a significant expansion of drought conditions.
Across the region, drought conditions improved in May as a result of beneficial precipitation. The High Plains region observed a 14 percent decrease in severe to exceptional (D2-D4) drought, there was also a 10 percent increase in areas that are not in any drought or abnormally dry conditions. After back-to-back months of well above-normal precipitation, North Dakota is now drought-free. Currently, only 12 percent of the state is in abnormally dry (D0) conditions. Conditions in South Dakota and Wyoming also improved significantly, with extreme drought (D3) and D2 reduced by 30 and 36 percent, respectively. While eastern Kansas is nearly free of drought, the western part of the state observed a 12 percent increase in D3 and D4 conditions. Colorado also recorded an 11 percent increase in D3-D4 conditions. Elsewhere in the region, other improvements and degradation were observed.
As described by the Western Regional Climate Center, a continuation from April of an active weather pattern in the Pacific Northwest persisted throughout May. Most of the Pacific Northwest saw above normal precipitation and the entire Pacific Northwest, northern California, and northern Great Basin saw below normal temperatures. The southern tier of the Southwest remained dry and warm with several large wildfires remaining active throughout the month in Arizona and New Mexico. The Calf Canyon and Hermits Peak fires both ignited in April in the Sangre de Cristo Mountains in northern New Mexico. Both fires remained active in May due to persistent hot, dry, and windy conditions and merged into one fire in mid-May that has grown to over 300,000 acres in size and became the largest fire in New Mexico history.
Oregon, Washington, and Idaho all had large areas with 150-200+ percent of normal precipitation for the month. In Seattle, Washington a trace or more of precipitation was recorded on 21 of 31 days in May with a total of 3.82 inches (97 millimeters), 203 percent of normal, and the second wettest since records began in 1945. Along the northern coast of Oregon, Astoria logged 6.24 inches (158.5 millimeters) at 184 percent of normal and coming in as the third wettest on record since 1953. A large swath of the Southwest recorded zero or trace amounts of precipitation in May including California from about the San Francisco Bay area southward, southern Nevada, southern Utah, all of Arizona, and much of New Mexico. May is climatologically a dry month for locations that received no measurable precipitation and most stations have seen several other years without any measurable precipitation in May.
According to the USDM at the end of May, 87 percent of the West was in drought with 38 percent of the West in extreme (D3) or exceptional (D4) drought. Reductions in drought severity and spatial extent were found in Oregon, Washington, Idaho, and southern Montana due in part to the cool and wet conditions during May. Most of the Southwest was already in drought at the start of May and spatial extent of area covered by any drought did not change; however, drought severity increased in California, Nevada, Utah, Arizona, and New Mexico.
Temperatures in Alaska were a mixed bag and were above normal in Southcentral, Southwest Mainland, and the North Slope, and below normal in the Northwest Arctic and Eastern Interior. Precipitation also varied by region with below normal in Southcentral, Southwest, and most of the Panhandle, and above normal in the Northwest Arctic and parts of the Interior. Anchorage was warm and dry with a temperature of 50.9 degrees Fahrenheit (10.5 degrees Celsius), +2.8 degrees Fahrenheit (+1.6 degrees Celsius) above normal for the third warmest on record, and total precipitation of 0.26 inch (6.6 millimeters), at 40 percent of normal and the 13th driest on record. Kodiak logged a temperature of 47.5 degrees Fahrenheit (8.6 degrees Celsius), +1.6 degrees Fahrenheit (+0.9 degrees Celsius) above normal and sixth warmest on record. Moderate drought (D1) was introduced into Southcentral Alaska for the first time since August, 2021. Snowfall in May at Denali National Park pushed the seasonal total to 176 inches making it the snowiest season since records began in 1922.
Precipitation anomalies were highly variable across Hawaii. On the Big Island it was wetter than normal on the northern and eastern parts of the island and drier on the southern tip. Hilo saw its 13th wettest May with 12.65 inches (321.3 millimeters) and 181 percent of normal. For O'ahu it was wetter than normal on the southern parts of the island and drier on the northern parts. Honolulu logged 1.4 inches (35.6 millimeters) at 171 percent of normal for the 14th wettest since records began in 1940. Overall, drought extent was reduced on most islands with 40 percent of Hawaii in moderate drought (D1) or worse at the end of May compared to 79 percent three months earlier.