The preliminary statewide average April temperature was 54.1 degrees, 1.5 degrees above the 1991-2020 average and tied for 28th warmest on record going back to 1895. The preliminary statewide average total April precipitation was 6.14 inches, 1.9 inches above the 1991-2020 average tied as 10th wettest on record statewide.
Data are provisional and may change slightly over time.
Summer or Winter? Why not Both?
April is a transition month in Illinois, moving us from winter to summer. As with most years, last month gave us a taste of all seasons. Daily average temperatures in and departures from normal from Peoria show the ups and downs typical of April temperatures (Figure 1). The daily average temperature in Peoria went from 73 degrees on April 16 to 43 degrees on April 20th.
April average temperatures ranged from the high 40s in northern Illinois to the low 60s in southern Illinois, between 1 and 4 degrees above normal (Figure 2). The prolonged period of warm weather in the middle of the month broke 14 daily high maximum temperature records and 22 daily high minimum temperature records in the state. Meanwhile, the brief shots of colder air in April broke nine daily low maximum temperature records and six daily low minimum temperature records.
Most places saw highs briefly reach into the mid-80s in the middle of the month, and a few stations around the St. Louis Metro East area flirted with 90 degrees. In contrast, most places in northern Illinois saw several nights with low temperatures dipping well into the 20s, including 21 degrees in Elgin on April 20th. Stockton was the coldest place in the state last month with an average temperature of 48.9 degrees, and Olmsted was the warmest place with an average temperature of 61.7 degrees.
Overall, the warmer parts of the months outweighed the colder parts, and the preliminary statewide average April temperature was 54.1 degrees, 1.5 degrees above the 1991-2020 average. If this average temperature is made official, it would be tied for 28th warmest on record going back to 1895.
April Showers
Last year April failed to bring its notorious showers and set in motion an early growing season drought in parts of Illinois. This year though, April did not disappoint those few rain lovers out there. An active storm track brought multiple waves of storms and rain across Illinois and made for the wettest month we’ve seen so far in 2024.
April total precipitation ranged from around 3 inches in northeast Illinois to over 10 inches in southwest Illinois (Figure 2). Most of the state between Interstates 88 and 64 was 1 to 5 inches wetter than normal last month, while far southern Illinois and the northern half of Chicagoland were within 1 inch of normal April rainfall. Highland in Madison County took the April precipitation crown with 9.58 inches total, the third wettest April on record there.
April added to what has been a very wet start to the year for parts of northern Illinois, especially along the Interstate 80 corridor. For example, Morris has already had 15.33 inches of precipitation in 2024, the second wettest start to a year on record there. Abundant spring rain has pushed several rivers over flood stage, including the Illinois River at Havana which spent all but a few days in April above minor to moderate flood stage.
Overall, the preliminary statewide average total April precipitation was 6.14 inches, 1.9 inches above the 1991-2020 average. If that number is made official, last month will be tied as 10th wettest on record statewide.
More Snow No One Wants
The first 80-degree day in many parts of Illinois is on par with any of the great weather gifts we have, like a Christmas morning snow or an October afternoon with winds below 20 mph. But if you’ve lived in Illinois for more than a year, you should be weary of the snow that inevitably follows that first taste of summer temperatures. Alas, a storm system snuck measurable snow into northern Illinois on April 2nd and 3rd. Totals ranged from just over a tenth of an inch as far south as Peoria to over 4 inches in eastern Jo Daviess County.
Thankfully, the latter half of the month came without measurable snowfall, leaving most of the state south of Interstate 74 snowless for April (Figure 3). I will not pronounce the snowfall season to be over as that would only doom us for a rare (but possible) May snow. I will say that the likely end-of-season snowfall in Illinois is only near to above normal in the northwest corner, thanks to a very heavy January snowstorm. Meanwhile, the northeast part of the state was 10 to 20 inches below normal snowfall in the 2023-24 snow season.
Outlooks
Even though April can give us a taste of summer, May is the first month where we really experience summer weather. Last year’s May was the driest statewide since 2012, but May outlooks from the Climate Prediction Center show highest chances for near to above normal precipitation this month in Illinois (Figure 5). There remain higher chances of above normal temperatures in May as well.
Outlooks for the period from May through July looks similar, with highest chances for above normal temperatures and precipitation to kick off the growing season (Figure 6).
