Frost line depth in Calhoun County, MI
How deep the ground freezes in Calhoun County, MI
32 in. Dig to 33 in, just below the frost. Nearest NOAA station: Battle Creek Kellogg Ap, 13 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.