Fall Brings Cooler, Below-normal Temperatures

After summer-like temperatures last week, fall came in full force during the last week of September. A cold front moved across the region early in the week. Before doing so, 48 stations in the southern Midwest broke or tied daily maximum temperature records (Figure 1). Average temperatures were near normal in the west to as much as 6°F below normal in the east (Figure 2). Region-wide, all states averaged below-normal temperatures for the week. Illinois had the largest temperature departure (-4.1°F), followed by Ohio (-3.8°F), Indiana (-3.7°F), Michigan (-3.6°F), Kentucky (-3.5°F), Wisconsin (-3.5°F), Iowa (-2.6°F), Missouri (-1.4°F), and Minnesota (-0.7°F). Maximum temperatures had the largest departures, especially in the eastern Midwest, where temperatures were more than 6°F below normal (Figure 3). Minimum temperatures also ran below normal for nearly the entire Midwest (Figure 4). Portions of Kentucky, Missouri, Illinois, Iowa, Minnesota, Wisconsin, and Michigan all saw their first 32°F temperature this week (Figure 5). There were 36 minimum and 35 maximum daily low temperature records broken or tied this week (Figure 6).

Widespread Below-Normal Precipitation

Dry weather continued for most during the last week of September. All states averaged below-normal precipitation (Figure 7) with most locations seeing less than 0.5 inches of rain (Figure 8). Kentucky averaged 11 percent of normal precipitation, which was the driest compared to normal in the Midwest. Six of the nine Midwestern states received less than 40 percent of normal precipitation (Kentucky, Illinois, Indiana, Iowa, Missouri, and Wisconsin). Several stations across the Midwest recorded in their top 10 driest Septembers on record as indicated by the Southeast Regional Climate Center’s Climate Perspectives Tool (Figure 9). Many streams and rivers continued to report below-normal streamflows across the Midwest, but especially in Iowa, Missouri, north-central Illinois, northern Indiana and other isolated locations across the Midwest (Figure 10). Despite the widespread dryness, there were some locations in Michigan and northeastern Ohio that received higher rain totals. Kalkaska County, located in northern Michigan, recorded 3.23 inches of rain, which was 2.03 inches above normal for the week. Northeastern Ohio’s Lake County measured 4.87 inches of rain, which was 3.77 inches above normal. On September 26, 3.15 inches fell. Thirteen stations across the Midwest, most concentrated in northern Michigan and northeastern Ohio, broke or tied daily precipitaiton records.

Storm Reports

There were 3-hail and 40-wind storm reports this week (Figure 11). Most of the storm reports occurred on September 25 in Michigan and Wisconsin. Four of these reports had confirmed wind gusts that were between 60-62 mph. Accompanied by these winds were several downed trees and powerlines.

Drought Monitor Update

As dry conditions continued across the Midwest, the September 27 US Drought Monitor indicated an 8.82 percent increase in the Midwest land in a drought category compared to the previous week (Figure 12). Exceptional Drought (D4) was added to southwest Missouri, which was the first time since 2012 this part of the state had D4 drought. The last occurrence of D4 anywhere in the Midwest was September 14, 2021 in northern Minnesota. Expansion of the Extreme Drought (D3) areas in southwest Missouri and northwest Iowa occurred. Severe Drought (D2) also expanded in central Missouri and northwest Wisconsin. Moderate Drought (D1) areas in western Minnesota, Missouri, western Kentucky and southern Illinois also expanded. Abnormally dry (D0) was also added and expanded in Kentucky, Illinois, and Indiana this week.