Frost line depth in St. Louis city, MO

How deep the ground freezes in St. Louis city, MO

18 in. Dig to 19 in, just below the frost. Nearest NOAA station: St Louis Sci Ctr, 1.5 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.