April 24 | Climate Review and Weather Update

by Trent Ford, State Climatologist
ISWS PRI University of Illinois

Another very spring-like week across the state, with average temperatures ranging from the mid-50s in northern Illinois to the low 60s in southern Illinois, between 2 and 5 degrees above average. April to date has been 5 to 8 degrees warmer than average, and a top 10 warmest April on record statewide. Despite the warmth, nighttime temperatures did dip below freezing in northern and central Illinois a couple of times this week, including lows of 24 degrees in Elgin and 25 in Rockford. For context, the average last spring freeze date is early
April in southern Illinois, mid-April in central Illinois, and right about now in northern Illinois. So, that means that half of the years in the last few decades have had a freeze after this date in places north of I-80.

We had another very active weather week, with multiple rounds of storms and heavy rain. 7-day precipitation totals ranged from less than a quarter of an inch in southeast Illinois to just over 3 inches in parts of northern and western Illinois. Much of northern Illinois and southern Wisconsin has received more than 10 inches of precipitation since the start of March, making it the wettest start to spring on record throughout that region. The result has been widespread significant flooding on mainstream rivers including the Fox and Des Plaines. The Fox River at Algonquin is expected to crest on Friday or Saturday at major flood stage, the highest crest since the historic floods of 2017. While flooding has been less of an issue in central Illinois, severe weather made its imprint this week. A major tornado outbreak across the state last Friday night produced dozens of twisters, including two damaging tornadoes in the Bloomington-Normal metro area. Illinois’ preliminary tornado count for this year is already around 100, making 2026 the third consecutive year toping the century mark for tornadoes. Prior to 2024, only one year on record had 100 tornadoes, making this an unprecedented period of severe weather activity.

Looking ahead, we will have another very active weather week. Multiple rounds of storms are expected, including significant risk of severe weather on Monday, especially for southern and central Illinois. 7-day precipitation totals range from over 2 inches in far southern Illinois to around 1 inch in northern Illinois. The rain could be beneficial to parts of southern Illinois that have gone too long without substantial rain; however, most folks in northern Illinois would prefer not to see rain again until after Memorial Day. Interestingly, outlooks for the first week of May show best chances of below average temperatures statewide. So, again, be careful planting vulnerable plants and keep your eye on the forecasted lows in case we approach that freeze mark again.