DeKalb County Climate
DeKalb County, Illinois
NOAA NCEI 1991-2020 Climate NormalsAvg Annual Temp
48.2°F
Annual Precip
37.6"
Annual Snowfall
33.9"
Extreme Heat Days
11
days >= 90°F/yr
Monthly Temperature
Precipitation Calendar
Growing Season & Gardening
5b
Minimum winter temperature range for plant survival
2,848
Supports most vegetables & fruits
Seasonal Overview
National Comparison
7-Day Outlook
Forecast
Current Conditions
Air Quality
Safety
Weather Alerts
Climate Advisory: DeKalb County
Climate Verdict
DeKalb County has a cool, averaging 48.2°F annually, moderate rainfall of 37.6 inches per year, rare extreme heat with only 10.75 days above 90°F annually, moderate snowfall of 33.9 inches annually. This climate profile shapes everything from energy costs to outdoor recreation opportunities.
Seasonal Breakdown
Winters are very cold — January averages 20.8°F. summers are warm — July averages 72.1°F. Residents experience a substantial 51°F difference between winter and summer.
Outdoor & Gardening Guidance
Growing season and gardening data is currently limited for DeKalb County. Check the USDA Plant Hardiness Zone Map and local extension office for specific guidance.
Regional Context
DeKalb County is 4.6°F cooler than the Illinois statewide average of 52.8°F, it is somewhat drier than average for Illinois, the county experiences 16.511032196969698 fewer extreme heat days than the state average.
Climate Profile
About DeKalb County Weather
Colder and Snowier Than National Norms
DeKalb County has an average annual temperature of 48.2°F, which is significantly cooler than the national median. It receives 33.9 inches of snow per year, making it a true northern climate.
One of the State's Cooler Counties
DeKalb's average temperature of 48.2°F sits well below the Illinois state average of 52.8°F. This reflects its position in the northern third of the state where winters are more intense.
A Northern Illinois Climate Anchor
Compared to southern Illinois, DeKalb is much cooler and sees nearly double the snowfall of central counties. It aligns closely with the weather patterns of neighbor Kane County.
Biting Winters and Mild Summers
January temperatures average a cold 20.8°F, while July peaks at a comfortable 72.1°F. The county only experiences about 11 days above 90°F, offering relief from the extreme heat found further south.
Prepare for the Long Winter
Reliable snow removal equipment and high-efficiency heating are essential for the 33.9 inches of annual snow. Residents should also insulate pipes to withstand the average 23.9°F winter temperatures.
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.