Rock Island County Climate
Rock Island County, Illinois
Avg Annual Temp
50.6°F
Annual Precip
37.8"
Annual Snowfall
36.1"
Extreme Heat Days
20.233333333333334
days >= 90°F/yr
Monthly Temperature
Precipitation Calendar
Seasonal Overview
National Comparison
Climate Profile
About Rock Island County Weather
A Cooler Northern Continental Climate
Rock Island County averages 50.6°F annually, which is cooler than the national median temperature. The region is defined by its strong seasonal contrasts and significant winter snowfall.
Colder and Drier Than Average
The county's 50.6°F average is over 2 degrees cooler than the Illinois state average of 52.8°F. It receives 37.8 inches of annual precipitation, which is drier than the state average of 41.7 inches.
The Snow Capital of the Region
Rock Island receives a staggering 36.1 inches of snow, far more than any other county in this group. It also sees only 20 days of extreme heat, making it much milder in summer than southern Illinois.
Heavy Snow and Mild Summers
Winters are harsh with a January average of 22.5°F and over 3 feet of total snowfall. Summers are pleasant, featuring a July average of 74.9°F and only 20 days of temperatures above 90°F.
Prepare for Serious Snowfall
A high-quality snow blower and cold-weather vehicle prep are mandatory for the 36.1 inches of annual snow. Home insulation should be a priority to combat the sub-freezing January averages.
Frequently Asked Questions
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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.