**Unseasonably Cool Temperatures **

It was a cool start to the first month of meteorological fall. Average temperatures were 10-12°F below normal to the northwest in northern Illinois, Iowa, Minnesota, and Wisconsin (Figure 1). Elsewhere, temperatures were still a solid 5-9°F below normal for the week. This was one of the coldest starts to September for many reporting locations in the Midwest. In Des Moines, Iowa, this was the fifth coldest first week of September since records began in 1878. In the Twin Cities, it was also the fifth coldest start to September since records began there in 1872.

Minimum temperatures were similarly anomalous with most of the region 5-10°F above normal (Figure 2). In a large swath through the middle of the region, minimum temperatures averaged up to 12°F above normal. In Flint, Michigan, a minimum temperature of 36°F was observed on September 7, which was only the third time temperatures dropped to 36°F or below in the first seven days of the month since records began in 1921. In Rockford, Illinois, the average minimum temperature for the week was 45.9°F, which was tied with 1909 for the coldest average low temperature for the first week of September since records began in 1893.

Maximum temperatures were 10-14°F below normal across much of Minnesota and Wisconsin (Figure 3). Most of the region was 5-10°F below normal. Temperatures particularly struggled to rise each day across the Upper Midwest. In Minnesota, both Hibbing and International Falls—which have records dating back to 1938 and 1897, respectively—observed four consecutive days, September 3-6, with maximum temperatures below 60°F during the first week of September. This has only happened once before at both locations—in International Falls in 1926, and in Hibbing in 1956. In Marquette, Michigan, the maximum temperature only rose to 50°F on September 6, which has only happened twice before during the first week of September in 1986 and 2024.

Precipitation/Drought

Most of the region saw below normal precipitation. This was the case for most areas along either side of the Mississippi River, where there was less than 25 percent of normal precipitation for the week (Figure 4). In Ohio and Indiana, precipitation was subpar at 25-50 percent of normal. Only in Kentucky, Michigan’s UP, northern Minnesota, and northern Wisconsin was precipitation near or above normal. While no measurable snow was reported, a snow/rain mixture was reported via social media on Michigan’s Keweenaw Peninsula on September 4.

As of September 2, the drought continued to expand with increasingly dry conditions in place. 14 percent of the region was experiencing D1 (moderate drought), and nearly 50 percent were under D0 (abnormally dry). Conditions largely went unchanged across the Upper Midwest, and the greatest expansions of D1 were made across southern Missouri, Kentucky, and southern Ohio (Figure 5).

Severe Weather

It was a relatively quiet week for severe weather, with generally dry and cooler conditions in place. On September 4, a brief tornado touched down in a cornfield in Nicollet County, Minnesota, damaging the roof of a building. On September 5, there were isolated storms across southern and eastern Kentucky that produced quarter-size hail and gusty winds.