Johnson County Climate
Johnson County, Illinois
Avg Annual Temp
57.9°F
Annual Precip
49.4"
Annual Snowfall
7.2"
Extreme Heat Days
41.3
days >= 90°F/yr
Monthly Temperature
Precipitation Calendar
DryWet❄= snowfall
❄4.2"
❄3.9"
❄4.8"
5.2"
4.9"
4.1"
3.3"
3.0"
3.4"
❄4.0"
4.4"
❄4.2"
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Seasonal Overview
National Comparison
Warmer than 64% of US counties
Wetter than 73% of US counties
More seasonal variation than 55% of US counties
Frequently Asked Questions
What is the average temperature in Johnson County?
The average annual temperature in Johnson County, IL is 57.9°F, based on NOAA 30-year climate normals (1991-2020).
How much rain does Johnson County get?
Johnson County receives an average of 49.4 inches of precipitation per year, including both rain and meltwater from snow. This is based on NOAA 30-year climate normals.
Does it snow in Johnson County?
Yes, Johnson County receives an average of 7.2 inches of snowfall per year according to NOAA climate normals.
How hot does Johnson County get in summer?
The average summer temperature (June-August) in Johnson County is 77.3°F. The county experiences an average of 41.3 days per year above 90°F.
How cold are winters in Johnson County?
The average winter temperature (December-February) in Johnson County is 37.4°F. January, typically the coldest month, averages 34.6°F.
Track your own weather in Johnson County
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Data source: NOAA National Centers for Environmental Information (NCEI), U.S. Climate Normals 1991-2020.
Climate normals are 30-year averages of weather variables computed from 1991 to 2020. Station data is aggregated to county level using spatial averaging. Data is informational only — not a substitute for official National Weather Service forecasts or emergency weather warnings.