Frost line depth in Ulster County, NY
How deep the ground freezes in Ulster County, NY
44 in. Dig to 45 in, just below the frost. Nearest NOAA station: Slide Mtn, 9.1 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.