Frost line depth in Lake County, MI
How deep the ground freezes in Lake County, MI
43 in. Dig to 44 in, just below the frost. Nearest NOAA station: Wellston 1n, 17.7 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.