Frost line depth in Platte County, NE
How deep the ground freezes in Platte County, NE
34 in. Dig to 35 in, just below the frost. Nearest NOAA station: Columbus 3 Ne, 12.4 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.