September 1-7, 2024

Temperatures

Average temperatures were below normal across the region to start September (Figure 1). They were most below normal in southeastern Iowa, northeastern Missouri and parts of Illinois, where average temperatures were as much as 6-7°f below normal for the week. Elsewhere, they were a standard 1-3°F below normal.

Minimum temperatures were more anomalous, with some areas west of the Mississippi River over 8°F below normal (Figure 2). After a cold front swept through early in the week, temperatures dropped well below normal for most areas. By September 7, minimum temperatures were still below normal, especially in Iowa, where Mason City Municipal Airport observed a minimum temperature of 38°F on September 7, the earliest temperature that low since 2011. La Crosse, Wisconsin also recorded a daily record low minimum temperature of 40°F, which was the earliest 40°F reading in September since 1986.

Maximum temperatures were below normal, though slightly less so than minimum temperatures (Figure 3). The Ohio Valley was generally near normal, but much of Illinois, Iowa, and the upper Midwest were 3-6°F below normal. Midland, Michigan recorded a maximum temperature of 58°F on September 7, which was only the second time the temperature dropped that low during the first week of September since records began in 1970.

Precipitation/Drought

Precipitation varied across the region this week, with little to no appreciable precipitation through the mid and upper Mississippi River Valley (Figure 4). Elsewhere in the region, there was 50 percent of normal precipitation, except eastern Kentucky and eastern Ohio, where precipitation did hover near 100 percent of normal.

Drought continued to expand over southeastern Ohio, where D4 (exceptional drought) covers the largest portion of the state since the Drought Monitor started in 2000. D1 (moderate drought) was expanded over western Ohio, eastern and southern Indiana, western Kentucky, and the Greater St. Louis area (Figure 5).

Severe Weather Given the quieter and cooler pattern this week, there was little severe weather. There were 21 storm reports total, 19 of which were wind reports (Figure 6). There was 1 tornado report in Porter County, Indiana, where a waterspout moved ashore into Indiana Dunes State Park.