Warm May Wraps Up Very Mild Spring

This spring was the fourth warmest start to any year on record in Illinois, and the summer has a high chance of above normal temperatures, according to Illinois State Climatologist Trent Ford at the University of Illinois’ Illinois State Water Survey.

Only 1921, 2012 and 2017 surpass 2024 for January to April temperatures. May continued the warm pattern across the state, though Illinois largely escaped early season extreme heat experienced in 2021 and 2022, making for largely pleasant temperatures last month.

Each of the three spring months brought average temperatures that were 2 to 6 degrees above normal. It was a top five warmest spring on record throughout virtually the entire state, including the 3rd warmest on record in Chicago and the 2nd warmest on record in Peoria.

The preliminary statewide average May temperature was 66.7 degrees, 3.5 degrees above the 1991-2020 average and the 11th warmest on record going back to 1895. The preliminary statewide average total May precipitation was 4.85 inches, 0.08 inches above the 1991-2020 average and the 42nd wettest on record statewide.

May average temperatures ranged from the high 50s in northern Illinois to the low 70s in southern Illinois, between 2 and 4 degrees above normal. Several stations saw their first 90-degree temperatures last month, including 91 degrees in Monmouth and at Chicago’s Midway Airport. Meanwhile, the state was largely spared a late spring freeze in May, with only a handful of stations experiencing temperatures below 40 degrees.

Overall, the warmest place in the state last month was Du Quoin, with an average temperature of 72.5 degrees, and the coldest place in the state was Mundelein with an average temperature of 59.2 degrees.

Last month precipitation was variable across Illinois, with extremely wet conditions in far southern Illinois and near to slightly drier than normal conditions in central and northern Illinois. Specifically, total May precipitation ranged from around 3.5 inches in west-central Illinois to nearly 10 inches in parts of southeast Illinois. Most areas south of Interstate 64 were 1 to 4 inches wetter than normal last month, while areas farther north were near to 1-2 inches drier than normal.

Much of last month’s precipitation came from thunderstorms that also brought severe weather to Illinois. The NOAA Storm Prediction Center listed 24 tornado reports, 153 severe wind reports and 56 severe hail reports in Illinois in May.

Climatological spring was wetter than normal for the entire state, with most of the state receiving 1 to 4 inches more than normal.

The Climate Prediction Center’s June one-month outlook for Illinois is not clear, but the summer season outlooks for June through August show higher chances of above normal temperatures. For precipitation, Illinois is squeezed between a band of expected drier than normal conditions to the west and wetter conditions to the east. This often, but not always, corresponds with active stormy weather in the summer.

For more information about monthly Illinois weather summaries, current conditions, and climate, visit the Illinois State Climatologist website.