Frost line depth in Florida

Most states leave the frost-line cell blank for local jurisdictions to fill in. Florida fills it in with NA. The Florida Building Code, Residential, marks both winter design temperature and frost line depth as not applicable across the whole state, which is a genuine published answer rather than an absence of one.

So the number that governs a Florida water service line is the general minimum: 12 inches below grade, with no frost line to sit below. That is shallow enough that the depth question in Florida is really a question about mechanical protection, tree roots and future landscaping rather than about freezing.

None of which means Florida has no winter plumbing problem. The panhandle freezes; the peninsula occasionally does. What it means is that the problem is never the buried line and always the exposed one: an outdoor shower, a pool equipment pad, an uninsulated pipe on the outside of a block wall, a well pump house.

Across all 139 Florida stations with published normals, the median first 32°F night falls around January 6 and the median station records 0 nights a year below 20°F, which is the coldest threshold NOAA counts and a decent proxy for a hard freeze rather than a light frost. The state’s spread runs from CRESTVIEW BOB SIKES AP, where the median first freeze is November 12, to EVERGLADES CITY 5 NE at January 20.

Florida’s statewide median first freeze falls in early January and the median station records fewer than four nights a year below freezing and none at all below 20°F. The spread runs from Crestview in the panhandle, whose median first freeze is 12 November, to Everglades City at 20 January. Miami International publishes no first-freeze normal at all, which is the record’s way of saying it does not reliably freeze there.

Where these numbers come from

The Florida frost figure was researched against the body that publishes it, and it’s recorded with a confidence note of “state code, verified” in our source ledger. Freeze dates are NOAA normals for stations in the state, picked by a fixed rule rather than by hand: first-order stations, spread west to east. The full method is on our methodology page.

• Freeze dates and cold-night counts: NOAA NCEI U.S. Climate Normals, 1991 to 2020, annual and seasonal by station. Retrieved 2026-09-09. Field definitions are in the by-variable readme.
• ZIP code locations: U.S. Census Bureau 2023 ZIP Code Tabulation Area gazetteer, matched to the nearest station by great-circle distance.
• 2023 Florida Building Code, Residential, 8th Ed., Ch. 4 Foundations (R403.1.4, R403.1.4.1) The Florida frost depth figure and basis.
• 2023 Florida Building Code, Residential, 8th Ed., Ch. 3 Building Planning, Table R301.2(1) (Frost line depth = NA) The Florida frost depth figure and basis.
• 2023 Florida Building Code, Residential, 8th Ed., Ch. 26 General Plumbing Requirements (P2603.5 Freezing) The Florida frost depth figure and basis.
• 2021 International Residential Code, Section P2603.5 (Freezing), ICC free code viewer The water service line burial rule.

The full method, including how we pick a station and what we do when there is not one close enough, is on our methodology page.