Temperatures

Temperatures were above normal across the region (Figure 1). Temperatures were 12-15°F above normal across Missouri, southern Iowa, and Illinois. Heading north and east, temperatures averaged 9-12°F above normal. Across eastern Kentucky, Ohio, Michigan, and northern Minnesota, temperatures averaged 3-9°F above normal.

Minimum temperatures were 12-15°F above normal across much of Iowa, northern Illinois, northern Missouri, and northwestern Indiana (Figure 2). Much of the region observed minimum temperatures 9-12°F above normal. Departures were lower in Kentucky, northern Michigan, and Minnesota, where minimum temperatures were generally 3-9°F above normal. Many places, particularly across the lower Midwest, observed record-high minimum temperatures. In St. Louis, September 2-5 marked 4 consecutive days of minimum temperatures above 80°F, the longest stretch of minimum temperatures above 80°F in September since records began in 1874. In Chicago, minimum temperatures remained above 75°F for 4 consecutive days, September 1-4, making it the longest stretch of 75°F+ minimum temperatures after September 1 since records began in 1871.

Maximum temperatures were particularly anomalous across Missouri, where they were up to 18°F above normal. Minimum temperatures were 12-15°F above normal across much of Iowa, northern Illinois, northern Missouri, and northwestern Indiana (Figure 3). Much of the region was 10-15°F above normal, though to the far north and east across Ohio, Michigan, and northern Minnesota, some places were only 3-6°F above normal. In Springfield, Missouri, maximum temperatures at or above 98°F were observed for 6 consecutive days, September 1-6, which is the longest stretch of such heat in September since records began in 1888. In fact, temperatures at or above 100°F were observed in Springfield from September 5-6, the second occurrence of consecutive 100°F days in September on record and the first 100°F+ temperatures in September since 2011.

Precipitation/Drought

With high pressure dominating many places from I-80 southward, precipitation was negligible or nonexistent across southeastern Iowa, Illinois, Missouri, Indiana, and western Kentucky Minimum temperatures were 12-15°F above normal across much of Iowa, northern Illinois, northern Missouri, and northwestern Indiana (Figure 4). Precipitation was seen north of the ridge across western Iowa, Minnesota, Wisconsin, Michigan, and Ohio. Precipitation was over 400 percent of normal along Wisconsin’s lakeshore north of Milwaukee and across northwestern Iowa.

As of September 1, drought expanded, with nearly 30 percent of the region in D1 (moderate drought) and at least 15 percent in D2 (severe drought). In southern Missouri, D1 and D2 expanded in coverage (Figure 5). Drought conditions remained largely unchanged across the Upper Midwest (Figure 5).

Severe Weather

There were over 300 reports of severe weather this week. 319 were wind reports, 39 were hail reports, and 2 were tornado reports (Figure 6). The largest outbreak was late on September 2 into September 3 across Michigan and Ohio. The first round on September 2 spawned an EF0 tornado in St. Clair County, Michigan, as well as hail up to 2 inches in diameter near Saginaw, Michigan. Storms continued on September 3, including an EF2 tornado with peak winds of 115 mph in Detroit, the first confirmed tornado within city limits since 1997. At least 300,000 power outages were reported during both days. On September 6, severe weather in Missouri produced 2-inch hail in Daviess County.