Lake Forest Illinois Climate Data

Monthly Average Climate Data for Lake Forest Illinois

Switch Data to Celsius/Metric Units
MonthAvg. LowAvg. HighAvg. Precip
January16.8 °F30.8 °F2.13 in.
February19.7 °F34.3 °F2.06 in.
March28.5 °F44.2 °F2.32 in.
April38.2 °F55.3 °F4.2 in.
May48.5 °F66.7 °F4.71 in.
June58.5 °F76.8 °F4.29 in.
July65.2 °F81.7 °F4.03 in.
August64.7 °F80.3 °F3.95 in.
September56.9 °F73.6 °F4.18 in.
October44.8 °F61.5 °F3.4 in.
November33.3 °F47.7 °F2.75 in.
December23.0 °F36.2 °F2.09 in.
Annual41.5 °F57.4 °F40.11 in.

Climate Data for Lake Forest Illinois

Average First Frost DateOct. 21 - Oct. 31
Average Last Frost DateMay 1 - May 10
Average Days With Frost100-125 Days
Plant Hardiness Zone - 2023Zone 6a : -10°F to -5°F
Plant Hardiness Zone - 2012Zone 5b : -15°F to -10°F
Current Drought ConditionsNormal
Köppen Climate ClassificationDfa - Humid Continental Hot Summers With Year Around Precipitation