Standard Illinois Climate Data

Monthly Average Climate Data for Standard Illinois

Switch Data to Celsius/Metric Units
MonthAvg. LowAvg. HighAvg. Precip
January15.1 °F31.2 °F1.77 in.
February18.5 °F35.7 °F1.75 in.
March28.4 °F48.1 °F2.4 in.
April39.0 °F61.4 °F3.46 in.
May50.8 °F72.6 °F4.53 in.
June60.7 °F81.4 °F4.3 in.
July64.1 °F84.3 °F3.83 in.
August61.9 °F82.5 °F3.72 in.
September53.7 °F77.0 °F3.39 in.
October42.2 °F64.5 °F2.93 in.
November31.0 °F49.3 °F2.45 in.
December20.9 °F36.4 °F1.95 in.
Annual40.5 °F60.4 °F36.48 in.

Climate Data for Standard Illinois

Average First Frost DateOct. 11 - Oct. 20
Average Last Frost DateMay 1 - May 10
Average Days With Frost125-150 Days
Plant Hardiness Zone - 2023Zone 5b : -15°F to -10°F
Plant Hardiness Zone - 2012Zone 5b : -15°F to -10°F
Current Drought ConditionsModerate Drought
Köppen Climate ClassificationDfa - Humid Continental Hot Summers With Year Around Precipitation
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