Entire Midwest Experienced Above Normal Temperatures, Broken Records

Warmer temperatures returned this week as the entire Midwest observed temperatures that were more than 2°F above normal (Figure 1). Western locations were the warmest with temperatures averaging 8-10°F above normal. Western Missouri saw temperatures up to 12°F above normal and the entire state averaged 10.3°F above normal for the week. Jasper County, Missouri averaged a maximum temperature of 94°F, minimum temperature of 70°F, and an average temperature of 81.7°F. On September 21, Jasper County tied the September 20, 1954 record of 99°F. Maximum temperatures (Figure 2) and minimum temperatures (Figure 3) showed a similar pattern, but maximum temperatures were more extreme. Locations in the upper Midwest had pockets of minimum temperatures averaging 8-10°F above normal. There were 257 maximum and 101 minimum daily high temperature records broken or tied (Figure 4). Most of the temperature records occurred in the western Midwest, but there were several high minimum temperature records in Michigan. MPR chief meteorologist, Paul Huttner, tweeted that Twin Cities & Minnesota experienced their longest summer on record by the most consecutive 70°F days.

Variable Precipitation Continued

Most of the Midwest experienced below normal precipitaiton, but isolated areas in northern Minnesota, Upper Peninsula Michigan, southeastern Iowa, northeastern Missouri, and central Illinois, saw in excess of 150 percent of normal precipitation (Figure 5). West-central Illinois, Climate Division 3, averaged 239 percent of normal precipitaiton and southeastern Iowa, Climate Division 9, received 193 percent of normal precipitation for the week. A bullseye of 1.5 to over 5 inches of rain fell near the Missouri, Iowa, and Illinois border (Figure 6). Lucas County, Iowa, measured 5.28 inches of rain this week, with 5.23 inches falling on September 18. For the past month, Cincinnati, Ohio has experienced the third most measurable rainfall events on record. There were 42 daily precipitaiton records that were broken or tied this week (Figure 7). Most records occurred near the Missouri, Iowa, and Illinois border. Kentucky was the driest state as the state received 7 percent of normal precipitation. Areas in Kentucky, Missouri, northern Michigan, southeastern Minnesota, and west-central Wisconsin missed out on measurable precipitation. Streamflows were largely near normal across the Midwest, with below normal readings concentrated in southeastern Iowa, eastern Michigan, northwestern Indiana, and southeastern Minnesota (Figure 8). Heavy rains in Chicago from the previous week contributed to the above normal streamflows in southeastern Wisconsin and northern Illinois.

Severe Weather Returned

After a week of no severe weather, storms returned from September 17-21 (Figure 9). There were 134 total reports (1-tornado, 75-hail, 58-wind).

• September 17 - there were several hail reports through Iowa and Minnesota. The largest (3.50 inches in diameter) occurred in Pottawattamie County, Iowa, with reports of broken car windows and substantial damage throughout Carson, Iowa. Accompanied with the hail, Pottawattamie County estimated winds at 70 mph.

• September 18 - an EF-0 tornado was confirmed in McLean County, Illinois on September 18. Damage was reported to mobile homes, duplexes, and trees. Additional hail reports occurred in Iowa, Illinois, and Missouri (largest 2.5 inches in diameter). A personal weather station measured a 72-mph wind gust in McLean County. NWS Chicago tweeted about the storms.

• September 20 – two reports of 3.0-inch diameter hail occurred in St. Croix, Pierce, and Juneau Counties in Wisconsin. There were reports of downed trees in Illinois and a roof lifted off a barn in Champaign County, Ohio.

• September 21 – there 17 wind reports across Illinois, Indiana, Kentucky, Michigan and Ohio where trees and powerlines were downed. A 58-mph wind gust was recorded in Bay Park, Michigan. An apartment building roof was damaged in St. Clair County, Illinois.

Drought Monitor Update

The September 20 US Drought Monitor brought improvement to the Extreme Drought (D3) in southeastern Iowa, but worsening of drought conditions in other locations (Figure 10). Missouri saw expansion of Abnormally Dry (D0), Moderate Drought (D1), and Severe Drought (D2). Southern Minnesota and western Wisconsin saw expansion of the D2 and a degradation of the D1 to D2. Overall, there was a 5.43 percent increase in land in a drought category (D0-D3) this week.