Frost line depth in Cook County, IL

How deep the ground freezes in Cook County, IL

28 in. Dig to 28 in, just below the frost. Nearest NOAA station: Chicago Northerly Is, 3.2 mi.

Your building department sets the legal frost line depth (IRC Table R301.2(1)); footings must go below it (R403.1.4.1). Call them before you dig.

Code depth · Snow