Midwest Weekly Highlights - May 25-31, 2021

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Cooler Temperatures Return

Temperatures were cooler than normal across the entire Midwest during the last week of May (Figure 1).  The coldest areas were in the Upper Midwest, where parts of Iowa, Minnesota, Wisconsin and Michigan were 4-7°F below normal.  Most of the Ohio River Valley was 1-2°F below normal, with some areas in western Missouri 3-6°F below normal. Late-season freezes were also recorded in the Upper Midwest, with most of northern Minnesota and the western U.P. of Michigan below 30°F on the morning of May 28 (Figure 2).  Freezing temperatures also reached southern Wisconsin and scattered areas of northern Iowa on the morning of May 29 (Figure 3).  These freezes were near the record latest for many in southern Wisconsin and northwestern Iowa (Figure 4).  Maximum temperatures were more on the extreme end, however (Figure 5).  Of the more than 500 daily low records recorded across the Midwest, more than 350 were from low maximum temperatures (Figure 6).
 

Scattered Showers and Thunderstorms

Precipitation was scattered across the Midwest with stronger showers and thunderstorms impacting two main areas of the region (Figure 7). More than an inch of rain fell from northwestern Iowa through western Wisconsin, with areas in southwestern Missouri receiving more than 1.50 inches.  These were the only two areas with significantly above-normal precipitation (Figure 8).  Meanwhile, much drier weather was observed in the Ohio River Valley, the northern Great Lakes and the west-central part of the region.  Areas in Minnesota and the U.P. of Michigan received less than a quarter of the normal amount.
 

Severe Weather in Missouri, Illinois and Wisconsin

Storms on May 25 and May 27 led to strong winds and hail in Missouri, Illinois and Wisconsin (Figure 9).  On May 25, a line of storms impacted northern Wisconsin, with winds up to 60 mph.  Isolated hail was also reported.  Trees and power lines were damaged along the line which moved into the western U.P. of Michigan.  On May 27, storms formed across southern Missouri, with strong winds up to 66 mph recorded.  Several brief tornadoes were also reported, which uprooted several trees and damaged hay bales.  Hail up to 1.75 inches was also reported.
 

Drought Continues to Expand

With drier weather impacting areas of the Midwest throughout the spring, drought continued to expand through the end of May (Figure 10).  According to the June 1 U.S. Drought Monitor, 18 percent of the Midwest was in drought, with severe drought nearing 3 percent of the region.  Severe drought expansion was most pronounced in southeastern Wisconsin and the northern suburbs of Chicago.  Lack of rainfall has been pronounced from northern Iowa through the U.P. of Michigan during the spring (Figure 11), leading to drier soils and lower streamflow as water demand increased.
 

-BJP-