Frost line depth in Clarke County, VA
How deep the ground freezes in Clarke County, VA
10 in. Dig to 12 in, the 12 in code minimum. Nearest NOAA station: Mt Wx 3, 6.2 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.