During the past week, the contiguous United States exhibited significant regional temperature anomalies driven by a highly amplified synoptic pattern.
Early in the period, a pronounced unseasonable cold air mass influenced the Northern Plains, Upper Midwest, and Northeast, depressing temperatures 5 to 15 degrees below normal across the Dakotas, Minnesota, New York, and Pennsylvania. Conversely, the Southwest and south Texas experienced anomalous warmth, with maximum temperatures exceeding 90 degrees and averaging up to 15 degrees above normal.
Precipitation during this period was characterized by severe convective outbreaks and pronounced moisture disparities. In the early portion of the week, persistent onshore moisture transport resulted in heavy rainfall totals of 4 to 6 inches across the central Gulf Coast.
Between May 17 to 18, a powerful frontal system traversing the central U.S. triggered widespread severe weather across the Great Plains and Midwest. This system produced damaging winds up to 80 mph, large hail, and multiple tornadoes across South Dakota, Nebraska, Iowa, Kansas, and Missouri, alongside localized flash flooding.
In contrast, extreme moisture deficits persisted west of the Rocky Mountains, where weekly precipitation totals generally remained under 0.10 inches, further elevating wildfire risk across the southern High Plains.
The U.S. Drought Monitor is jointly produced by the National Drought Mitigation Center at the University of Nebraska-Lincoln, the U.S. Department of Agriculture and the National Oceanic Atmospheric Administration. (Map courtesy of NDMC.)
South
Below-normal precipitation dominated the South. The vast majority of Texas, Oklahoma and Arkansas received less than 0.1 to 0.5 inches of total rainfall, leaving nearly the entire geographic footprint under exceptionally dry conditions.
This lack of rainfall translated into widespread departures ranging from 0.75 to 1.50 inches below normal. Below-normal rainfall totals resulted in the introduction of exceptional drought in the Oklahoma Panhandle and D4 expansion in parts of Arkansas and Mississippi. Extreme to severe drought were expanded in parts of Oklahoma and Arkansas.
The major exception to this dry regime was concentrated in southern portions of the region, specifically southern Texas, where localized convective storms delivered 1 to 3 inches of rainfall, resulting in the improvement of extreme drought in southern portions of Texas. Temperatures were above normal across much of the region, ranging from the upper 50s and low 60s in Tennessee to the upper 80s in parts of Texas. Looking at departures from normal, a highly anomalous zone of intense warmth gripped the western half of the region, where temperatures averaged 6 to 15 degrees above historical norms.
Midwest
Precipitation patterns across the Midwest were defined by an intense, localized corridor of heavy rainfall contrasting with widespread dryness elsewhere.
The most significant hydrological activity occurred across southern Iowa, and northern and central Missouri, where a series of storm complexes dropped widespread totals of 2.5 to 5.5 inches, with a localized amounts exceeding 6.25 inches in south-central Iowa and north-central Missouri. This wet weather pattern resulted in substantial positive departures of 1.5 to over 4.5 inches above normal.
Conversely, the northern and eastern fringes of the region experienced a remarkably dry week. Northern Minnesota received less than 0.5 inches of rain.
Anomalous warmth dominated the Midwest with average temperatures ranging from the upper 40s along the Canadian border to the 70s in southwestern Missouri. Looking at departures from normal, unseasonable warmth dominated the western and central Midwest.
A broad area encompassing Missouri, Iowa and Minnesota reported temperatures 2 to 6 degrees above historical norms, with the core of the warmth centering over western Iowa and northwest Missouri at 6 to 10 degrees above average.
High Plains
Temperatures were above normal across much of the region, with average readings ranging from the low 40s along the Canadian border and in the mountains to the mid-70s across southern Kansas. Highly anomalous early-season warmth gripped the southern half of the region.
The core of this heat anomaly was centered over Kansas and Colorado, where weekly temperatures soared 6 to 12 degrees above historical averages, with localized spots in southern Kansas peaking more than 12 degrees above normal. This unseasonable warmth extended moderately northward into Nebraska, yielding departures of 3 to 6 degrees above average.
Conversely, the northern High Plains remained under a more seasonal air mass; North Dakota, South Dakota and northern Wyoming experienced below-normal conditions, fluctuating within 3 to 6 degrees of historical baseline temperatures. Precipitation amounts varied across the region, with extreme dryness across the much of the region and a highly concentrated deluge along the southeastern boundary.
Large portions of Wyoming, Colorado, and western parts of North Dakota, South Dakota, Nebraska, and Kansas, reported weekly totals below 0.5 inches, with extensive areas receiving less than 0.1 inches. This lack of moisture resulted in departures of 0.5 to 1.5 inches below average, causing conditions to deteriorate.
Extreme drought expanded in southwestern Kansas and southern Colorado. Severe drought was occurring in parts of Colorado and northeast Wyoming, while moderate drought expanded in parts of South Dakota.
In powerful contrast, intense convective activity generated a sharp corridor of heavy rainfall across eastern portions of Kansas and Nebraska. Totals in this localized zone rapidly climbed between 2.5 and 5.5 inches, with departures ranging between 1.5 to over 4.5 inches above normal, resulting in improvements to moderate to exceptional drought in Nebraska and moderate to extreme drought in Kansas.
Heavy rainfall also brought improvements to severe to exceptional drought in northern Colorado and a reduction of exceptional drought in southern Wyoming.
West
Temperatures varied across the region, with average readings ranging from the mid-30s and 40s across the northern tier and high elevations to the low 80s in the desert Southwest.
In terms of departures from normal, unseasonably cold conditions dominated the northern half of the region, with departures ranging between 3 to 9 degrees below normal. In sharp contrast, the southern tier experienced unseasonable warmth.
A building ridge over the Southwest drove temperatures in New Mexico 3 to 9 degrees above normal, with eastern New Mexico seeing the greatest extremes. Precipitation across the western region was characterized by an extreme contrast between a highly active storm track in the Pacific Northwest and aridity across the remainder of the region.
Above-normal precipitation was confined to parts of Montana, where weekly rainfall totals ranged between 1.5 to 3.5 inches, with localized totals in the Cascade Range exceeding 4.5 inches. This activity generated substantial departures of 0.75 to over 30 inches above normal, justifying moderate to severe drought and abnormal dryness improvements in Washington and northern Idaho, and improvements to abnormal dryness to northwestern Oregon and western Montana.
Conversely, dry conditions persisted across nearly the entire remaining geographic footprint. Widespread areas across New Mexico, and parts of ] Montana recorded negligible rainfall totals of less than 0.1 inches. Due to the climatological onset of the dry season in parts of the West, this lack of rainfall translated into modest negative departures ranging from near-normal to 0.75 inches below seasonal averages.
Nonetheless, deteriorating conditions led to the expansion of extreme drought in parts of New Mexico and Montana. In addition, severe drought was expanded in Montana while moderate drought expanded in parts of Montana.
Looking ahead
Over the next five days (May 19 to 23), the U.S. can expect a highly dynamic weather pattern characterized by contrasting temperature extremes and widespread storm activity.
An early-season heatwave will make headlines across much of the eastern U.S. through midweek, with interior portions of the Mid-Atlantic and the Carolinas seeing highs climb into the lower to middle 90s—warm enough to potentially establish new daily records before a cold front brings cooler relief by Thursday.
In stark contrast, the Intermountain West and Rockies will experience below-normal temperatures to start the week, alongside late-season accumulating snow in the higher elevations of Colorado and Wyoming. Meanwhile, a strong cold front tracking across the Plains and Midwest will spark widespread showers and severe thunderstorms.
Multiple rounds of heavy rainfall will bring a risk of scattered flash flooding, focusing heavily on Texas, Oklahoma, and Arkansas on Tuesday before an expanded risk of heavy precipitation stretches from western Texas to the central Appalachians on Wednesday.
Further out, the Climate Prediction Center’s 6- to 10-day outlook (valid May 24 to 28) favors above-normal temperatures across most of the U.S.—stretching from the Rocky Mountains all the way to the East Coast, with the highest confidence for this unseasonable warmth concentrated in the Upper Midwest.
Meanwhile, near-normal temperatures are forecast in parts of the South and along the West Coast. Probabilities for wetter-than-average conditions favor the vast majority of the country. In the contiguous U.S., this wet weather pattern extends from the Southwest to the East Coast, with the greatest probability of above-normal precipitation expected to be in the south-central U.S., specifically across southern Texas.
The northern Rockies and northern parts of the Midwest are favored to receive near-normal precipitation during this time. No areas are favored to be drier than normal.
Rocky Bilotta is with NOAA and NCEI.
