Mild May wraps up otherwise warm spring in Illinois

Yahoo

21-06-2025

Despite milder May temperatures, the spring season was still a top-10 warmest on record in many places in the Midwest, including in St. Louis, Peoria, and Paducah, according to Illinois State Climatologist Trent Ford at the Prairie Research Institute.
The first four months of 2025 collectively were just under 1 degree warmer than normal statewide. May temperatures varied within 1 degree of normal statewide, with periods of much warmer and much cooler weather during the month. March temperatures were 4 to 8 degrees above normal, and April temperatures were 1 to 3 degrees above normal.
In recent years, early spring warmth has pushed spring phenology ahead of normal, increasing the risk of frost or freeze damage to tender perennials and horticultural crops. However, a colder winter this year helped extend dormancy a bit later, resulting in a timely spring phenology and good prospects for fruit and berry crops this year.
May average temperatures ranged from the mid-50s in northern Illinois to the high 60s in southern Illinois. Several stations saw their first 90-plus degree temperatures, including a daily record-breaking 94 degrees at Chicago's O'Hare Airport on May 15. 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 preliminary statewide average May temperature was 63.0 degrees, 0.2 degrees below the 1991-2020 average and the 58th warmest on record.
While last month's precipitation was typically variable across Illinois, May was overall drier in most places. The preliminary statewide average total May precipitation was 3.75 inches, 1.02 inches below the 1991-2020 average and the 55th driest on record statewide.
May precipitation ranged from around 2 inches in the Chicagoland area to nearly 8 inches in far southern Illinois. Most areas south of Interstate 70 were near to slightly wetter than normal, while most of northern and central Illinois were 1 to 3 inches drier than normal.
Spring precipitation ranged from around 6 inches in far northern Illinois to over 20 inches in southern Illinois. The northern half of the state was 1 to 2 inches drier than normal, while southern Illinois was 2 to 8 inches wetter than normal. It was the fourth wettest spring on record in Salem and the fifth wettest spring in Centralia.
May was very active on the severe weather front. The NOAA Storm Prediction Center listed 23 tornado reports, 92 severe wind reports, and 61 severe hail reports in Illinois. Among these include an EF-4 tornado in Williamson County, and 2-inch hail in Morgan and Sangamon Counties.
Illinois set a new statewide tornado record in 2024, but is ahead of this time last year on statewide tornadoes, with 105 reports total.
Outlooks
June is the start of climatological summer and is an exciting month for many reasons. Warm weather is here, and schools are out. The Climate Prediction Center's June outlook shows the best chances of summer starting a bit on the warm side, with the best chance of near-normal precipitation and maybe a continued wetter trend in southern Illinois.
The summer season outlooks (June through August) also show higher chances of above-normal temperatures this summer. For precipitation, Illinois is squeezed between a band of expected drier-than-normal conditions to the west and wetter conditions to the east. That 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. Data are provisional and may change slightly over time.
The Prairie Research Institute at the University of Illinois Urbana-Champaign provides scientific expertise and transformative research to the people of Illinois and beyond. PRI is home to the five state scientific surveys: the Illinois Natural History Survey, Illinois State Archaeological Survey, Illinois State Geological Survey, Illinois State Water Survey, and Illinois Sustainable Technology Center.