Temperature

The average May temperature for the Midwest was 61.0°F, which was 1.3°F above the 1991-2020 normal (Figure 1). Average temperatures in the far eastern region were slightly below normal, while areas west of the Mississippi River were up to 9°F above normal (Figure 2). Maximum (Figure 3) and minimum (Figure 4) temperatures followed a similar west-to-east spatial pattern. Statewide average temperatures ranged from 1.7°F below normal in Ohio to 4.5°F above normal in Minnesota. Statewide, Minnesota recorded the 6th warmest May since 1895. No monthly average, maximum, or minimum temperature records were broken among long-running stations across the Midwest in May. Three stations in Minnesota ranked in the top ten warmest for May, including Minneapolis-St. Paul, which recorded the 6th warmest May in 151 years. The average spring (March-May) temperature for the Midwest was 0.1°F below normal (Figure 5), with most areas near to slightly above normal, except in Minnesota, where temperatures were up to 4°F below normal for spring (Figure 6).

Precipitation

May precipitation totaled 2.31 inches for the Midwest, which was 2.07 inches below normal, or 53 percent of normal (Figure 1). The Midwest recorded the 7th driest May since 1895. All nine Midwestern states measured below-normal precipitation, with totals ranging from 1.41 inches below normal in Minnesota to 2.57 inches below normal in Missouri. Rankings indicate the 4th driest May on record for Wisconsin, with statewide precipitation at 40 percent of normal for the month. Most of the region had precipitation ranging from 10-75 percent of normal for May (Figure 7), and many stations ranked in the top ten driest for the month. Murray, Kentucky, had the driest May in 94 years, with 0.41 inches of precipitation. Ashland, Wisconsin, had the driest May in 113 years with 0.31 inches. Still, localized thunderstorms produced isolated areas with near- to above-normal precipitation. For instance, Comfrey, Minnesota, had over 10 inches of precipitation, which was nearly 6 inches above normal for May. Southern Minnesota and Michigan’s Upper Peninsula were two locations where 100-175 percent of normal precipitation spanned multiple counties (Figure 7). Spring (March-May) precipitation for the Midwest totaled 8.55 inches, which was 2.07 inches below normal (Figure 5). The driest area in the region spanned from central Missouri northward through Iowa, where precipitation departures were 4-9 inches below normal for spring (Figure 8).

Drought

Rapid drying occurred across much of the Midwest throughout May due to the combined effects of below-normal precipitation and an unusually dry atmosphere (low humidity). By month’s end, abnormal dryness and drought spread across two-thirds of the Midwest and affected all nine states in the region (Figure 9). Drought was widespread in Missouri, with 50 percent of the state in moderate to extreme drought and 30 percent depicted as abnormally dry (Figure 10). Missouri’s Governor declared a Drought Alert on May 31 as farmers and ranchers reported high demand for hay and low forage quality. Persistent drought conditions prompted water restrictions in western Iowa. Low atmospheric humidity, low rainfall, and a delayed spring green-up increased fire risk, prompting the National Weather Service to issue two dozen Red Flag warnings throughout the month in northern Minnesota and northwest Wisconsin.

Air Quality

Historically large wildfires in Alberta, Canada, brought smoky and hazy conditions to the Midwest starting in early May that persisted throughout the month. As the smoke settled in, repeated air quality alerts were issued across multiple Midwestern states, with the greatest number of alerts issued in Minnesota and Wisconsin.

Record May Snowfall in the Upper Peninsula

A stalled low-pressure system from late April lingered around the Great Lakes region at the start of May, bringing heavy snowfall to Michigan’s Upper Peninsula and light snow to eastern Wisconsin. Herman, Michigan, recorded a storm total (April 29-May 2) snowfall of 52 inches (Figure 11), with a single-day snowfall total of 27 inches on May 2 (Figure 12). According to the National Weather Service in Marquette, Herman set a new record for the greatest one-day May snowfall east of the Mississippi River. Herman also achieved its snowiest May on record with 48 inches, beating the previous record by 22 inches.

May 1 Dust Storm

Strong winds (gusting up to 54 mph) moved across freshly plowed fields on May 1, resulting in an isolated but significant dust storm over a two-mile stretch of Interstate 55 near Springfield, Illinois. Near-zero visibility led to a 72-vehicle crash that resulted in 7 fatalities and 37 injuries.