Frost line depth in Santa Clara County, CA

How deep the ground freezes in Santa Clara County, CA

9 in. Dig to 12 in, the 12 in code minimum. Nearest NOAA station: Mt Hamilton, 8.8 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.