Frost line depth in Alger County, MI
How deep the ground freezes in Alger County, MI
46 in. Dig to 47 in, just below the frost. Nearest NOAA station: Munsing Lakeshore, 7.3 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.