May 22-31, 2023

Hot and Dry for Most

Strong upper-level troughing this week led to hot conditions and limited precipitation throughout the region. Minnesota’s temperatures were most above normal, averaging 6.6°F above normal, but reached up to 12°F above normal in the north (Figure 1). The far southern Midwest recorded near or slightly below normal temperatures; on average, Kentucky’s temperatures were 1.6°F below normal. Average maximum temperatures were well above-normal for every state, except eastern Kentucky, where temperatures of up to 4°F below normal were observed (Figure 2). On the contrary, average minimum temperatures were only above normal in the northwest corner of the Midwest; the rest of the region’s minimum temperatures were slightly below normal (Figure 3). There were 28 high maximum and two high minimum temperature records broken or tied this week, as well as 22 high minimum and 10 low maximum records (Figure 4a, Figure 4b).

Much of the Midwest was completely dry this week and totals in areas that did receive precipitation were below normal, for the most part (Figure 5a). Small bullseyes and gradients of above-normal to normal precipitation were observed in northern Minnesota, far western Missouri, and far eastern Kentucky (Figure 5b). This was, or tied for, the driest week on record at all but a handful of Midwestern stations (Figure 6).

Diurnally-driven convection caused some pop-up storms throughout the week. Storms that developed in Minnesota on May 29 were slightly more severe, as hail of up to two inches in diameter was observed; this activity continued overnight and lingered through the early morning. Storms fired up the following day along a surface boundary positioned near the western border of the Midwest (Figure 7a, Figure 7b, 5/30 5pm EDT, NCEI/WPC). These storms weakened overnight, but more precipitation developed and remained stagnant over the Kansas City metro area throughout the morning (Figure 8, 5/31 8am EDT, NCEI). The Kansas City International Airport recorded 2.69 inches of rain throughout the week.

Streamflow and Drought Conditions Worsen

The combination of the lack of precipitation, warm temperatures, and low dewpoints caused streamflow and drought conditions to worsen significantly this week. When compared to last week, streamflow values have either decreased or remained the same throughout the Midwest (Figure 9). Rivers in cental and northeastern Missouri, central Iowa, northeastern Illinois, southeastern Wisconsin, and southern Kentucky were classified at low levels.

After this week, only 34 percent of the Midwest was free of dryness or drought (Figure 10). Abnormal dryness (D0) has been expanded to blanket the Midwest. D1 (moderate drought) conditions were added in northeastern Iowa and central Illinois, and were expanded in Missouri, southern Iowa, and the Chicago metro area. D2 (severe drought) conditions were expanded in western Iowa and northern Missouri. D3 (extreme drought) conditions were added in northeastern Missouri, and expanded in central Missouri.