Temperatures

Average temperatures were below normal to the east and above normal to the west (Figure 1). Much of Indiana, Kentucky, Ohio, and southeastern Michigan were 1-3°F below normal. In states west of the Mississippi River, average temperatures were 3-5°F above normal.

Minimum temperatures were significantly below normal across the east. Parts of Indiana, Kentucky, and Ohio were 5-9°F below normal for the week (Figure 2). Minimum temperatures were above normal across western Iowa, Minnesota, and northwestern Wisconsin. In Cleveland, Ohio, minimum temperatures were near 10°F below normal for the week. In Lansing, Michigan, a minimum temperature of 38°F on September 8 was the earliest temperature below 40°F since 2003. In Fort Wayne, Indiana, the temperature dropped to 36°F, the earliest temperature to drop that low in September since records began in 1897.

Maximum temperatures skewed above normal. Across western Illinois, Iowa, Missouri, and Minnesota, maximum temperatures were as much as 8-9°F above normal (Figure 3). Much of this warmth came later in the week as temperatures rebounded from an early-season cold front. Temperatures rose well into the 90s across Iowa and Missouri. In Quincy, Illinois, temperatures rose above 96°F on two consecutive days, September 13-14, for the first time in September since 2013. In St. Louis, Missouri, the temperature rose to 98°F on September 14, which was the warmest September temperature in St. Louis since 2013.

Precipitation/Drought

With hot and dry conditions under high pressure, precipitation was limited. Most places south of I-80 observed little to no precipitation. Only across Michigan’s Upper Peninsula (UP) and Minnesota’s Arrowhead region was precipitation near to above normal (Figure 4).

The rapidly drying conditions prompted the National Weather Service’s Climate Prediction Center to issue a hazards outlook for a rapid onset risk of drought for southern areas of the region. Drought expanded rapidly as of the September 1 update; nearly 50 percent of the region was classified as abnormally dry or D0 (Figure 5). Nearly 20 percent of the region was in moderate drought or D1, up over five percent from the prior week. The biggest expansions of drought have occurred over southern Illinois, southern Missouri, and Ohio.