Alton Illinois Climate Data

Monthly Average Climate Data for Alton Illinois

Switch Data to Celsius/Metric Units
MonthAvg. LowAvg. HighAvg. Precip
January23.1 °F39.0 °F2.59 in.
February26.5 °F44.5 °F2.31 in.
March35.3 °F54.7 °F3.32 in.
April46.1 °F66.4 °F4.7 in.
May56.9 °F75.6 °F5.17 in.
June66.1 °F84.4 °F4.3 in.
July69.7 °F87.5 °F3.95 in.
August67.7 °F86.5 °F3.62 in.
September59.3 °F80.3 °F3.31 in.
October47.7 °F68.6 °F3.3 in.
November36.5 °F54.8 °F3.53 in.
December27.7 °F43.7 °F2.65 in.
Annual46.9 °F65.5 °F42.75 in.

Climate Data for Alton Illinois

Average First Frost DateNov. 1 - Nov. 10
Average Last Frost DateApr. 11 - Apr. 20
Average Days With Frost75-100 Days
Plant Hardiness Zone - 2023Zone 7a : 0°F to 5°F
Plant Hardiness Zone - 2012Zone 6b : -5°F to 0°F
Current Drought ConditionsModerate Drought
Köppen Climate ClassificationDfa - Humid Continental Hot Summers With Year Around Precipitation