Frost line depth in Ida County, IA
How deep the ground freezes in Ida County, IA
43 in. Dig to 44 in, just below the frost. Nearest NOAA station: Ida Grove 5nw, 0.4 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.