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CHAMPAIGN, Ill. — April was colder than normal in Illinois, with freezing temperatures occurring into mid-month and as far south as St. Louis Metro East, according to Illinois State Climatologist Trent Ford at the University of Illinois’ Illinois State Water Survey.
Rainfall in April was frequent, but averaged near normal statewide for the month.
The preliminary statewide average April temperature was 49.6 degrees, 2.7 degrees below the 1991-2020 average.
April average temperatures ranged from the low 40s in northern Illinois to the mid-50s in southern Illinois, between 1 and 6 degrees below normal.
The coldest point in the state last month was Galena in Jo Daviess County with an average temperature of 40.8 degrees, which is 6 degrees below normal.
Precipitation
The preliminary statewide average total March precipitation was 3.74 inches, 0.06 inches below the 1991-2020 average.
For most of the state, the total amount of April precipitation was not excessive, and some areas were drier than normal. However, precipitation frequency was unusually high as most places recorded 12-plus days with some measurable precipitation.
Macomb had 22 days with measurable precipitation last month, Aurora had 20, Champaign had 19 and Cairo had 18.
Oddly, extremely frequent precipitation did not amount to extreme totals last month. Total April precipitation ranged from just under 3 inches in east-central Illinois to over 6 inches in far southern Illinois. Most areas north of Interstate 80 and south of Interstate 64 were 1 to 2 inches wetter than normal.
Meanwhile, despite many places in central Illinois having recorded 15-20 days with measurable precipitation last month, most of the central part of the state was near to slightly drier than normal.
The persistently wet and cool month did make quite an impact on drought conditions in northern Illinois.
Soil moisture and streamflow across northern Illinois have recovered to pre-drought conditions, and in response the U.S. Drought Monitor eliminated all drought across the state on April 26.
That ended a 55-consecutive-week stretch of some drought in Illinois, the longest in the 20-plus year Drought Monitor record.
Although the lack of extreme rainfall last month kept most serious flooding at bay, soils across the state remained wet due to frequent rain and cooler temperatures.
This caused fieldwork and planting delays, especially in southern Illinois, where conditions remain wetter than normal for this time of the year.
Snow in April stayed mostly north of Interstate 80. April snowfall totals ranged from just over a tenth of an inch along and north of Interstate 74 to over 3 inches around the Rockford area.
Snowfall for the October-April season ranged from just over 30 inches in northeast Illinois to less than 5 inches in far southern Illinois.
Most of the state had snowfall that was 5 to 15 inches below normal this season, except for a narrow band from Calhoun County to Will County, which had 1 to 10 inches above normal.
Outlooks
The most recent Climate Prediction Center outlooks for the month of May lean to below-normal temperatures persisting from April in northern Illinois, with an equal chance of above- and below-normal temperatures in central and southern Illinois.
However, the May-July outlooks begin to lean to warmer than normal temperatures to start summer, and these chances increase as we move into the heart of summer, June-August.
On the precipitation side, May outlooks lean a bit wetter than normal for western Illinois, but show equal chances of wetter and drier than normal rainfall for the rest of the state.
The May-July outlooks put Illinois between higher chances of drier conditions to our west and wetter conditions to our east.
As we move into summer, forecasts for June-August begin to move to higher chances of dry conditions farther east into western Illinois.