May 15-21, 2025

Cooler Temperatures Return

Temperatures were above normal by 3-6°F for much of the Ohio Valley and mid-Mississippi River Valley (Figure 1). Heading north and west, temperatures were near to below normal, especially over northwest Iowa and Minnesota, where they were 5-9°F below normal as cooler air entered the region.

Minimum temperatures were slightly below normal over western Minnesota (Figure 2). Elsewhere, minimum temperatures were generally above normal. In parts of Kentucky, minimum temperatures averaged nearly 8°F above normal for the week. In Youngstown, Ohio, a minimum temperature of 67°F was observed on May 16, which was the earliest in the calendar year a minimum temperature at or above 67°F was recorded in Youngstown.

Maximum temperatures started to change across the north as cooler air entered the region. Temperatures were anywhere from 5-15°F below normal across the Upper Midwest (Figure 3). In fact, parts of western Minnesota averaged nearly 20°F below normal. Meanwhile, south of I-80, temperatures were near to slightly above normal. In Madison, Wisconsin, the temperature rose to 87°F on May 15, which was the warmest temperature of the year thus far. This was followed only several days later by two consecutive days of maximum temperatures at 50°F, May 20-21, which was the coldest stretch of May high temperatures since 2010.

Precipitation/May 15-16 Severe Weather/Drought

Most of the region received above normal precipitation for the period, with over 200 percent of normal precipitation observed in many locations (Figure 4). In Minnesota, the western half of the state reported 300-400 percent of normal precipitation in spots. Most of the rain fell later in the period, and over 3 inches of precipitation occurred in the western suburbs of the Twin Cities from May 19-21, while much of the state received at least 2 inches.

There were over 1,000 storm reports for the third week of May, the most active week so far this year. There were over 900 straight-line wind reports, nearly 500 reports of hail, and over 100 reports of tornadoes (Figure 5). They were scattered throughout the region as a strong low pressure system sat nearly stationary over the region for several days. On May 15, tornadoes were reported in Illinois, Michigan, Minnesota, and Wisconsin, with Wisconsin alone reporting 15 tornadoes including 4 that rose to EF2 strength. An EF2 tornado affected parts of Dodge County with winds peaking at 120 mph, with severe damage to multiple homes in Mayville. This brought the total of tornadoes in Wisconsin this year up to 22, not far from the statewide annual average of 23.

The next day was followed by yet another outbreak, with an EF3 tornado traversing the northern portions of St. Louis, Missouri. That tornado spent 23 miles on the ground and crossed the Mississippi River into Illinois. There was also an EF4 tornado in southern Illinois not far outside of Carbondale. That tornado had peak winds of 190 mph and removed roofs off of homes, lifted a newly constructed two-story house off its foundation, and caused 7 injuries. More tornadoes affected Missouri on May 19, all of which were rated EF0 and EF1 and affected locations across the state from St. Joseph to St. Louis.

Drought didn’t change very much as the aforementioned precipitation was not fully observed by the May 20 update. Moderate drought (D1) slightly expanded over the Chicago area and the Illinois/Indiana border (Figure 6). Abnormally dry (D0) was removed from a good share of Iowa.

On May 16, dry antecedent conditions and heavy winds due to nearby severe weather caused a wall of dust to rush north through the Chicago metropolitan area. Dust storm warnings were issued for Chicago and surrounding areas, which is rare, and a dust storm of this magnitude had not impacted the area since the Dust Bowl. Farmers reported having to replant certain crops.