Frost line depth in Niagara County, NY
How deep the ground freezes in Niagara County, NY
28 in. Dig to 29 in, just below the frost. Nearest NOAA station: Youngstown 2 E, 10 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.