Frost line depth in McPherson County, SD
How deep the ground freezes in McPherson County, SD
59 in. Dig to 59 in, just below the frost. Nearest NOAA station: Aberdeen 35 Wnw, 6.4 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.