Frost line depth in Humboldt County, NV
How deep the ground freezes in Humboldt County, NV
20 in. Dig to 21 in, just below the frost. Nearest NOAA station: Orovada 3 W, 18.6 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.