Below-Average Temperatures for the Entire Midwest

It was a record-breaking start to the month, but temperatures dropped fast during the second week in September. Every state in the Midwest recorded an average temperature that was below normal for the period. Illinois had the largest temperature departure, coming in at 3.9°F below normal for the period. This was followed by Minnesota at 3.8°F below normal and Missouri at 3.5°F below normal. The smallest departure from normal was Kentucky, with an average temperature that was 0.8°F below normal. Parts of the Upper Midwest saw temperatures 5-7°F below normal, especially in Michigan, Wisconsin, and northern Minnesota (Figure 1).

Average minimum temperatures were well below normal for the period in the western Midwest. Minnesota, Iowa, and Missouri saw spots with minimum temperatures 5-7°F below normal (Figure 2). In fact, the average minimum temperature in a small section of far northern Minnesota was only 35-40°F (Figure 8). In Duluth, Minnesota, the minimum temperature bottomed out at 35°F on September 13, despite the normal minimum temperature being 48°F. Only ten days earlier, temperatures nearly hit the century mark in the Northland.

Maximum temperatures were most below normal in the Great Lakes. Certain areas of Wisconsin, Michigan, Ohio, Indiana and Illinois observed temperatures 7-10°F below normal (Figure 3). There were several days across Michigan’s Upper Peninsula where maximum temperatures did not reach 60°F. Marquette, Michigan did not see maximum temperatures hit 60°F from September 11-September 14, despite the normal maximum temperature being in the upper 60s.

Another Week, Another Precipitation Shortfall

The past week was again a largely dry and below normal for precipitation. Many areas saw less than 0.05” of rain for the week, including much of Kentucky, southern Indiana and southern Illinois (Figure 4). Some needed rain did fall right along the I-80 corridor from Chicago west into Iowa, with most areas receiving between 0.5-0.75” of rain.

Some of the driest and wettest weather actually occurred in Minnesota. While western Minnesota, including Moorhead, saw less than 0.05”, while the Greater Duluth area saw 1-2” for the week. Flash flooding from heavy rains on September 11 actually caused dirt from a construction project to flow downhill and pile up on a downtown thoroughfare.

Drought Continues Across the Region

Yet again, drought persisted and even expanded this past week. According to the latest drought monitor, at least two thirds of the Midwest is in abnormally dry (D0) conditions, which is an increase of 3.79 percent over last week. Dry conditions continue to work back eastward, with an expansion of moderate drought (D1) just north of Fort Wayne, Indiana (Figure 5). Drought conditions have been persistent for western parts of the region, including much of Missouri, Iowa, Minnesota, and Wisconsin. In some positive development, a small area of extreme drought (D4) was removed from far northwestern Wisconsin after heavy rains the week prior (Figure 6).

Frost and Freeze Season Begins

The growing season is still going strong in most of the Midwest. That being said, a couple spots saw temperatures within frost and freeze criteria. Minnesota’s Arrowhead region saw minimum temperatures fall down below the 32°F threshold early on September 13 and 14 (Figure 7). Hibbing, Minnesota recorded a temperature of 27°F on the morning of September 13. International Falls, Minnesota recorded a temperature of 31°F. Similar temperatures were recorded in remote parts of northern Wisconsin and Michigan’s UP. The first frost advisories of the season were issued for much of the Arrowhead region and northern Wisconsin for the morning of September 13, and for northern Lower Michigan and the UP during the morning of September 14.