Below Normal Temperatures in Midwest

The average temperature for the Midwest was 45.1◦F for April, which was 3.6◦F below the 1991-2020 normal. The Midwest had the 24th coldest April since 1895. Temperature departures were coldest in the north, although all nine states had below-normal temperatures (Figure 1). The statewide monthly average temperature ranged from 2.0◦F below normal in Kentucky to 6.1◦F below normal in Minnesota. Minnesota had the 10th coldest April on record, while Iowa was tied for 13th coldest and Wisconsin tied for their 16th coldest (Figure 2). A brief warm-up across the lower Midwest on April 23-25 pushed high temperatures over 80◦F and resulted in over 55 daily high maximum and 135 high minimum temperature records broken or tied (Figure 3). This was followed by a blast of unseasonably cold air across the upper Midwest on April 26-28 that resulted in 186 daily low minimum and 170 daily low maximum temperature records broken or tied (Figure 4).

Variable Precipitation across the Midwest

Average Midwest precipitation for April was 3.60 inches, which was 0.07 inches below normal, or 98 percent of normal. Statewide precipitation totals ranged from 1.03 inches below normal in Indiana to 1.30 inches above normal in Minnesota. Minnesota had the 7th wettest April on record since 1895. Conditions were persistently wet across the Midwest, even in locations with below-normal precipitation (Figure 5). Many stations reported measurable precipitation (greater than or equal to 0.01 inches) on 15 or more days during April (Figure 6), ranking among the top ten for the number of precipitation days (Figure 7). Many stations across the central Midwest received up to an inch of snowfall, with heavier totals in the north (Figure 8).

Improved Drought Conditions

Drought conditions improved throughout April, with about 2 percent of the region in drought and 10 percent showing abnormal dryness by the month’s end (Figure 9). Drought was confined to western Iowa while isolated pockets of abnormal dryness were reported across the upper Midwest and extreme eastern Kentucky.

Flooding in Minnesota

Melting snowpack combined with multiple rounds of heavy precipitation in northwest Minnesota contributed to major flooding on the Red River of the North during the last week in April (Figure 10). The river flood stage at Oslo, Minnesota reached a foot short of the record crest. The Minnesota National Guard was deployed to Crookston to assist with sandbagging and flood response.

Persistent Wind

While April tends to be a breezy month across the Midwest, this year was notably windy in the western and central Midwest. An analysis of 21 Iowa weather stations found that 20 had above-average wind speeds for April. Eighteen stations had their greatest number of hours (dating back 25 years) with April average wind speeds exceeding 20 mph, and eight stations had wind speeds sustained over 20 mph for 300 hours (42 percent of the month). Frequent high peak wind gusts were also notable across the region. Minneapolis, Minnesota reported 22 days with gusts over 35 mph, the most since 1973 by 8 days. St. Louis, Missouri had 15 days with gusts over 35 mph, the most since records started in 1973. Chicago and Indianapolis both had peak wind gusts above 35 mph on about half the days in April.

Notable Weather Events

A potent storm system brought severe weather to the Midwest on April 12 (Figure 11) and 13 (Figure 12). On April 12, ten confirmed tornadoes affected Iowa and Minnesota, including three rated EF-2, resulting in injuries and damage to property, trees, and powerlines. Eight weak tornadoes were confirmed on April 13 in Kentucky that caused downed trees and powerlines along with damage to buildings. Overall, there were 36 tornado, 244 hail, and 265 wind storm reports this month (Figure 13).