What to do for the best on the exterior of our house? Every county has those variations that have been recorded for some time and thus county records will show those zones that are hit hardest by extreme temperatures. These swells get even bigger as unfrozen moisture below them is drawn up to the cooler pockets. Back To Map California Extreme Frost Line Penetration (in inches) State Average Frost Depth: 5″ Source: U.S. Department of Commerce Detailed explanation: what is "dayspring"? Search for "frost line". I'm a professional carpenter in Raleigh, North Carolina. If frost heaves these footings, then whole portions of the structure above will be thrown out of whack. Frost heaving, which is the upward swelling of soil during freezing conditions, can move the foundations of buildings, severely damaging them. How is it possible that a