DeKalb County Climate
DeKalb County, Illinois
Avg Annual Temp
48.2°F
Annual Precip
37.6"
Annual Snowfall
33.9"
Extreme Heat Days
10.75
days >= 90°F/yr
Monthly Temperature
Precipitation Calendar
Seasonal Overview
National Comparison
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 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.