Cloudiness in Illinois

Illinois has never been considered the Sunshine State. However, cities in Illinois are considered in the middle ranks of U.S. cities in terms of cloudiness. They are neither as sunny as Las Vegas nor as cloudy as Seattle.

Here is a breakdown of the number days of clear, partly cloudy, and cloudy days for the few sites in Illinois with long-term observations. Hourly weather observations of cloud types and coverage (in tenths) are combined into daily values. The daily average sky cover is assigned to three classes. Daily average sky cover ranging from 0 to 3 tenths is considered “clear.” Daily average sky cover from 4 to 6 tenths is considered “partly cloudy”, and from 7 to 10 tenths is considered “cloudy.”

Annual Average Number of Days by City
Cairo 113 104 149
Chicago 84 105 176
Moline 101 100 164
Peoria 95 97 172
Rockford 93 98 174
Springfield 104 94 167

You can also visit the National Centers for Environmental Information for more information on cloudiness of U.S. cities.