Frost line depth in Teton County, ID
How deep the ground freezes in Teton County, ID
45 in. Dig to 45 in, just below the frost. Nearest NOAA station: Driggs, 5.4 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.