Near Normal August, Above Normal Summer Temperature

The average temperature for August in the Midwest was 71.4°F, which was 0.5°F above the 1991-2020 normal. Statewide average temperatures ranged from near normal in Illinois to 1.0◦F above normal in Iowa and Michigan (Figure 1). The summer temperature (June, July, August) for the Midwest was 0.8°F above normal, with areas in the west and south 1-4°F above normal and locations in the central region near normal (Figure 2). Numerous cities across the region recorded a top 10 warmest summer, including Detroit (Michigan), Toledo (Ohio), Chicago (Illinois), Louisville (Kentucky), and Springfield (Missouri) (Figure 3).

Precipitation

August precipitation was 3.95 inches for the Midwest, which was 0.28 inches above normal, or 108 percent of normal. Statewide precipitation totals ranged from 0.76 inches below normal in Iowa to 0.90 inches above normal in Kentucky. All states except Iowa had above-normal precipitation in August (Figure 4). Cincinnati, Ohio had the tenth wettest August since 1871. Summer (June-August) precipitation for the Midwest totaled 11.13 inches, which was 1.17 inches below normal. Generally, the western region had a dry summer while extreme wetness was reported across the south (Figure 5). The Minneapolis-St. Paul area recorded the 9th driest summer over the last 150 years. The St. Louis area had the 6th wettest summer over the past 149 years.

Severe Weather

Preliminary storm reports reveal August was quieter than usual across the Midwest (Figure 6). Preliminary tornado and hail reports were 38 percent and 55 percent of the 2000-2021 median, respectively, while preliminary wind reports were near normal. Despite the lull, there were several weather-related injuries and fatalities from fallen trees and lightning during August. Severe weather was relatively inactive this summer (June-August) across the Midwest, particularly for tornado and hail reports which were 60 percent and 55 percent of the 2000-2021 median. Preliminary wind reports for summer, however, were slightly above normal (103 percent of the median).

Drought

Increased widespread rainfall and moderated temperatures brought drought relief to many locations, but not all, across the Midwest throughout August (Figure 7). By month’s end, dryness and drought affected 28 percent of the region, down from 39 percent coverage at the start of August. Missouri, southern Illinois, and western Kentucky had rapid drought recovery whereas conditions worsened in Iowa and across the upper Midwest. Looking across summer (June-August), dryness and drought exhibited rapid onset and rapid recovery. Dry conditions affected just 9 percent of the Midwest to start summer, and conditions peaked weeks later with 50 percent of the region affected. As precipitation returned for some locations, summer ended with dryness or drought affecting 28 percent of the Midwest.

Flash Flooding in Southern Illinois

On August 2, heavy thunderstorms over Jasper County and surrounding areas in southern Illinois soaked the region with 7-10 inches of rainfall in just 24 hours (Figure 8). Flash flooding and river flooding affected nearby farm fields (Figure 9).

Flash Flooding in Northern Illinois

Two rounds of heavy rainfall on August 7-8 resulted in flash flooding across multiple northern Illinois counties (Figure 10). Storm event rainfall totals were 4-8 inches across a wide swath, with isolated higher amounts (Figure 11). Freeport, Illinois recorded a two-day rainfall total of 11.25 inches.