Frost line depth in Webster County, IA
How deep the ground freezes in Webster County, IA
45 in. Dig to 46 in, just below the frost. Nearest NOAA station: Ft Dodge 5nnw, 10.4 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.