May Temperatures Well Above Normal Statewide, Heavy Precipitation Hits Western Nebraska
The National Center for Environmental Information (NCEI) preliminary statewide rankings indicate that Nebraska experienced the 110th warmest and 30th wettest May since records began in 1895. NCEI indicates that the preliminary state average temperature for May is 62.0°F, which is 3.6°F above normal (based on the period 1991-2020). May precipitation on an area weighted basis was 4.60 inches according to NCEI, which is 1.10 inches above normal.
The U.S Drought Monitor depiction for May 30, 2023 indicates that extreme drought (D3) and exceptional drought (D4) are in place across central, south-central, east-central and northeast Nebraska. The core of the worst conditions (D4) lie in an area bounded by Grand Island/Hastings on the western edge, Clay Center to Crete on the southern edge, Grand Island to Norfolk on the northwestern edge and West Point to Crete on the southeast edge of the exceptional drought area. There has been a one- to two-category drought degradation across this area.
The rainfall across western Nebraska has led to at least a one-category improvement across the Panhandle, southwest, north-central and west-central climate districts. Drought conditions improved two categories in a small area of the southern Panhandle and the southern half of the west central climate district. Although the U.S. Drought Monitor shows at least a one-category improvement across the southwest climate district, the vast majority of this district experienced a two-category improvement. Monthly rainfall over nine inches brought a three-category improvement to all of Hayes County, eastern Chase and Dundy counties, northern Red Willow County and western Frontier County.
The average statewide precipitation value for May is 4.60 inches according to NCEI, which is 1.10 inches above normal according to the current 1991-2020 comparison period. Although May 2023 is currently ranked as the 99th wettest May since comparison records began in 1896, a breakdown of climate division rankings reveals a wide disparity of precipitation extremes. The Panhandle and southwest climate districts were ranked as the fourth- and second-wettest May’s on record, respectively. Conversely, the east-central and southeast climate districts were rated as the second and 12th driest May’s on record. Additional precipitation rankings for the remaining climate divisions (1= driest, 129 wettest) are as follows: North Central (115), Northeast (37), Central (101), South Central (75).
Almost every location reporting in real time across the western half of Nebraska received at least 3.50 inches during the month of May, with totals exceeding 10 inches in parts of Chase, Dundy, Frontier, Hayes, Hitchcock and Red Willow counties. Further east, less than 0.50 inches of moisture for the month of May were reported in northeastern Lancaster, southeastern Saunders and northwestern Cass counties, along with most of Sarpy and Dodge counties. For the month of May, precipitation surpluses exceeded 7.5 inches where the greatest moisture fell across southwest Nebraska, while monthly deficits exceeded 4.5 inches in a narrow band from Lincoln to Omaha.
Precipitation events during May were confined to three distinct periods — May 4-12, May 16-17 and May 25-30. During the May 4-12 period, an upper air trough situated over the Great Basin ejected pieces of energy that crossed the central and southern High Plains region. For Nebraska, these individual pieces of energy brought scattered thunderstorms on a daily basis to the western half of the state, while eastern locations were left high and dry until the main upper level low finally moved into the central Plains on May 12, triggering a widespread severe weather event to the state.
Severe thunderstorms broke out along a surface warm front pushing northward through the state during the afternoon of May 12. Storm spotters submitted 40 tornado sightings, 25 hail reports and 18 wind reports. After National Weather Service personnel conducted site review, it was determined that at least 19 tornadoes touched down, including eight EF1 and 3 EF2 tornadoes. An additional six tornado touchdowns were verified from storm events that were submitted for the month, bringing the confirmed tornado count for May 2023 to 25.
A quick-moving trough crossed the northern plains May 16-17 and scattered thunderstorm developed across the northern half of the state. Another upper air trough developed over the Great Basin May 25-30 and led to daily rounds of thunderstorms across western Nebraska. These thunderstorm events were unable to hold together and bring widespread moisture to the eastern third of Nebraska due to a blocking ridge of high pressure over the Great Lakes that spread dry Canadian air westward from southern and eastern Ontario.
Two locations in southwestern Nebraska that are NERain observers reported more than 14 inches of moisture for the month: McCook 5.4 SW (14.12 inches) and Palisade 2.4 WSW (14.11 inches). The highest totals reported by NWS cooperative observers reporting in real time were 12.94 inches at Max 13 N and the McCook Airport with 10.94 inches. The McCook Airport also reported the largest 24-hour precipitation total for NWS cooperative observers with 6.06 inches on May 26, while Palisade 2.4 WSW reported 7.47 inches for the highest NERain observer 24-hour total.
The only precipitation records reported from NWS airport locations were reported at North Platte and Valentine. North Platte reported 1.47 inches of moisture on May 4, which replaced the old record of 1.25 inches set in 1985. Another precipitation record was set at North Platte on May 12 when 1.33 inches was reported, which eclipsed the old record of 1.28 inches set in 2011. Valentine also set a daily precipitation record on May 12 when 0.93 inches of precipitation fell, breaking the old record of 0.84 inches set in 1942.
An examination of monthly May precipitation totals from NERain observers indicate that 10 locations reported more than 12 inches of moisture during the month, 24 locations reported more than nine and less than 12 inches, 26 location reported more than eight and less than nine inches, 31 stations reported more than seven inches and less than eight inches, and 39 station reported more than six inches and less than seven inches. On the flip side, a total of 57 locations reported more than 0.50 inches and less than an inch, 35 stations reported 0.25-0.50 inches and 12 stations failed to receive 0.25 inches for the month of May.
The highest liquid equivalent precipitation total report from real-time cooperative weather observers during April was 3.85 inches at Beatrice 1 N and Nebraska City 2 NW, while the greatest monthly NERain precipitation total was 4.65 inches at Louisville 1.4 W. The cooperative weather observer at Chadron 3 SW reported 14.5 inches of snowfall during April making it the highest monthly total submitted from National Weather Service observers, while the highest snowfall total reported through NeRain was at Crawford 10.8 ESE with 7.3 inches. A preliminary analysis of cooperative observer seasonal snowfall totals through April 30 indicates that at least 12 stations have reported over 60 inches of snowfall for season, with Chadron 3 SW leading the pack with 86.6 inches of accumulated snowfall.
Nebraska’s average temperature for May 2023 was 62.0°F, which is 3.6°F above normal. All climate divisions experienced above-normal temperatures during the month and were in the upper third of the distribution of historical May average temperature values. The climate division average temperature values, departure from normal, and ranking (1 = coldest, 129 = warmest) are as follows: Panhandle (58.9°F, +4.1°F, 117); north-central (60.8°F, +3.6°F, 111); northeast (64.0°F, +4.4°F, 118); central (61.9°F, +3.0°F, 105); east-central (65.2°F, +4.3°F, 113); southwest (61.6°F, +2.7°F, 98); South-central (63.2°F, +2.7°F, 101); southeast (64.7°F, +2.9°F, 105).
An examination of all available real-time temperature records available for May 2023 indicates that average temperature were greater than 4°F above normal across the northern Panhandle, the northwestern half of the Sandhill region, northeast Nebraska and the northern half of the east-central climate district. Conversely, average temperature departures were 1-2°F above normal across southwest and west-central Nebraska, as well as parts of the south-central and southeast climate districts.
No daily temperature records were submitted by the NWS for airport locations within the state this May. However, the warmest maximum temperature reported during the month was 94°F at two locations, Crete 4 ESE on May 31 and the Tekamah Airport on May 30. The coldest minimum temperature reported for May 2023 was 15°F reported at Agate 3 E on May 1, with the Alliance Airport reporting that second coldest minimum temperature of 20°F reported on May 2.
The Climate Prediction Center (CPC) released their official June climate outlooks on May 31, which indicates that there is a slight chance for above-normal precipitation for the southwestern third of Nebraska and a slight chance of below-normal temperatures across the southern third of the Panhandle and the southwestern corner of the state. A slight chance of above-normal temperatures is forecast for the northeastern half of Nebraska. For areas not mentioned, there are equal chances of receiving above normal-, normal, or below-normal temperatures and/or precipitation.
On a national scale, above normal temperatures are projected for the Pacific Northwest, northern Rockies, northern Plains, Great Lakes and the northeastern corner of the nation. Below-normal temperatures are projected for the southwest desert region, the central Rockies, the southern Great Basin and the western half of the southern High Plains region. Above-normal precipitation is forecast from California eastward through the central Rockies, along with the northern Rocky Mountain and southern High Plain. The highest odds of below-normal precipitation are indicated for the Great Lakes region, with a slight risk of below-normal moisture for the northeastern United States, along with the central and eastern Corn Belt.
Widespread above-normal moisture across the western third of Nebraska provided drought relief and eliminated precipitation deficits that had accumulated since the start of the soil moisture recharge period, which began at the beginning of October 2022. Accumulated precipitation totals during May ranged from eight to 12 inches across most of the southwestern climate district, while areas of east-central, south-central and southeast Nebraska received less than an inch of moisture. Precipitation surpluses since last October exceeded four inches across Dundy and Hitchcock counties at the end of May, while precipitation deficits exceeded eight inches centered on York and Filmore counties. A broad area extending from Grand Island to Omaha and from Norfolk south through Fairbury/Hebron have accumulated deficits of at least six inches for the same time period.
There were improvements to topsoil and subsoil moisture estimates during the month of May across western Nebraska, which was partially offset by dryness across the eastern third of the state. According to the Nebraska Agricultural Statistics Service (NASS), topsoil moisture was estimated to be 22% very short, 35% short, 39% adequate and 4% surplus on May 28. Compared to the final crop progress report issued on April 30, topsoil rated very short decreased 15 percentage points, while the short category shrank 6 percentage points. There was a 17-percentage point increase in the adequate category and a 4 percentage increase in the surplus category. It should be noted that topsoil estimates are likely wetter across the western half of the state, while eastern Nebraska is much drier due to below normal May moisture.
Subsoil moisture estimates for Nebraska also showed improvement, but at a more muted pace than the improvements to topsoil conditions. NASS reports that as of May 28, 39% of the subsoil moisture was rated very poor, 44% poor, 25% adequate and 0% surplus. There was a 15-percentage point decrease during May for subsoils rated very poor, while subsoils rated short increased 6 percentage points and those rated adequate increased 8 percentage points.
With warm-season crops still emerging at the end of May, crop conditions were generally favorable due to low water use demand. However, warm-season crop conditions will rapidly deteriorate as the month progresses if precipitation across the eastern half of the state is similar to what was received during May. There was a positive response to widespread moisture across western Nebraska as the condition of the wheat crop and pastures improved when comparing the final crop reports issued at the end of April and May.
NASS indicates that as of May 28, winter wheat was rated 18% very poor, 33% poor, 35% fair, 12% good and 2% excellent. There was a 5-percentage point reduction in the very poor category during the month, which was offset by a 5-percentage point increase in the poor category. Subsequently, winter wheat reported fair increased 11 percentage points, while the good category decreased 10 percentage points and the surplus category shrank 1 percentage point.
Pastures across western Nebraska showed a strong response to the generous moisture that fell across western Nebraska where a majority of the rangeland is located. NASS indicates that as of May 28 pastures were rated 19% very poor, 24% poor, 31% adequate, 24% good and 2% excellent. Compared to the first pasture condition report for 2023 for conditions through May 7, pastures rated very poor shrank 6 percentage points and those rated poor dropped 19 percentage points. Pastures rated fair increased one percentage point, while pasture rated good expanded 22 percentage points and those rated surplus increased 2 percentage points.
May Mesonet Extremes
- Highest Air Temperature: 93.6°F Memphis 5 N (May 30)
- Lowest Air Temperature: 17.9°F Whitman 5 NE (May 1)
- Highest Heat Index Temperature: 92.9°F Rulo 5 SW (May 6)
- Lowest Wind Chill Temperature: 14.1°F North Platte 3 SW (May 1)
- Maximum Wind Gust (three meters): 84.2 mph Hayes Center 3 N (May 6)
- Maximum Wind Gust (10 meters): 61.0 mph Keystone 4 W (May 11)
- Highest Daily Precipitation: 3.84 inches Hayes Center 3 N (May 27)
- Highest Four-Inch Soil Temperature: 96.6°F Lincoln 1500 N 45th (May 30)
- Lowest Four-Inch Soil Temperature: 39.7°F Fordyce 4 W (May 1)