Slightly Above Normal Temperatures

August temperatures averaged slightly above normal across most of the Midwest. Illinois, Iowa, Missouri, Kentucky, and Wisconsin were mostly within 2°F above normal with the remaining Midwestern states being warmer by 2-4°F above normal. Only parts of Michigan and a small area in northwestern Ohio was over 4°F above normal (Figure 1). There were 129 maximum daily high temperature records made across the Midwest, with most occurring on August 10th through 12th and August 24th through 26th. Maximum temperature departures ranged from 1-4°F above normal throughout much of Midwest (Figure 2), with Minnesota (35), Illinois (23), and Indiana (22) experiencing the most records. There were 556 maximum daily low temperature records during the month with the greatest impacts also felt during the same periods as the maximum high temperatures. Missouri had the most maximum daily low temperature records (134) followed by Iowa (72) and Michigan (71). Average minimum temperatures ranged from 1-5°F above normal, with isolated areas reaching 6°F above normal (Figure 3).

Variable Precipitation

Precipitation amounts varied from 1.5 inches to over 10 inches across the Midwest (Figure 4). The heaviest rainfall amounts occurred in a swath from southern Minnesota/northwest Iowa through central Wisconsin into east-central Michigan. The lowest precipitation amounts were in northern Minnesota, central Missouri, and central Illinois. These patterns translated to over 200 percent of normal in the wettest locations and 50 to 75 percent of normal in the driest regions (Figure 5). Regionwide precipitation was 4.16 inches which was 0.49 inches above normal. Statewide totals were below normal in Indiana (-0.27 inches) and Missouri (-0.81 inches) with the remaining states above normal, ranging from 0.19 inches in Illinois to 1.56 inches in Wisconsin (Figure 6). There were 392 daily high precipitation records in August with the 27th having the most at 48.

Drought Update

The area of Midwest affected by drought slightly increased in August from 34.7 percent to 38.3 percent (Figure 7). Most of Minnesota, Iowa, and the upper peninsula of Michigan were impacted with isolated areas along the Wisconsin-Illinois border and central Indiana. For the first time in the US Drought Monitor’s history (since 2000), Minnesota had areas in the D4-Exceptional Drought category, which is the worst category of drought. The Greenwood Lake Fire in Minnesota, which started on August 15th and continued into September, required dozens of residents to evacuate.

Elevated Storm Reports

Severe weather was reported on 24 of 31 days in August across the Midwest with all nine states impacted (Figure 8). Reports were double digits on 12 days and reached triple digits on 5 days. The busiest day of the month was on the 11th with most of the reports coming from Ohio (121) and Michigan (113) and were predominantly high wind reports. Tornadoes were reported on 8 days with the most active day being the 9th of August where 22 tornadoes were recorded, 18 of which were in Illinois. Most of the tornado activity in Illinois on that day occurred in Bureau and DeKalb counties. August 28th was the most active hail day across the Midwest (26 reports) where Minnesota (20 reports) had the most hail activity.