Rock Island County Climate
Rock Island County, Illinois
NOAA NCEI 1991-2020 Climate NormalsAvg Annual Temp
50.6°F
Annual Precip
37.8"
Annual Snowfall
36.1"
Extreme Heat Days
20
days >= 90°F/yr
Monthly Temperature
Precipitation Calendar
Growing Season & Gardening
5b
Minimum winter temperature range for plant survival
3,351
Supports most vegetables & fruits
Seasonal Overview
National Comparison
7-Day Outlook
Forecast
Current Conditions
Air Quality
Safety
Weather Alerts
Climate Advisory: Rock Island County
Climate Verdict
Rock Island County has a mild, with an average annual temperature of 50.6°F, moderate rainfall of 37.8 inches per year, occasional hot days — 20.233333333333334 per year above 90°F, moderate snowfall of 36.1 inches annually. This climate profile shapes everything from energy costs to outdoor recreation opportunities.
Seasonal Breakdown
Winters are very cold — January averages 22.5°F. summers are warm — July averages 74.9°F. Residents experience a substantial 52°F difference between winter and summer.
Outdoor & Gardening Guidance
Growing season and gardening data is currently limited for Rock Island County. Check the USDA Plant Hardiness Zone Map and local extension office for specific guidance.
Regional Context
Rock Island County closely matches the Illinois statewide average temperature of 52.8°F, it is somewhat drier than average for Illinois.
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 sources: NOAA National Centers for Environmental Information (NCEI), U.S. Climate Normals 1991-2020. Forecast and alert data from National Weather Service API. Air quality data from Open-Meteo.
Climate normals are 30-year averages of weather variables. Station data is aggregated to county level. Forecasts and alerts are fetched live and may change frequently. Data is informational only — not a substitute for official National Weather Service forecasts or emergency weather warnings.