Frost line depth in Texas

The honest answer for most of Texas is that frost depth is close to irrelevant, and the code reflects that. Dallas fills its climate table with 6 inches. Lubbock, three hundred miles northwest and three thousand feet higher, publishes 12. Half a foot separates the third-largest city in the state from the high plains, and there is no state table reconciling even that, because Texas does not impose one. The panhandle proper, where the earliest first freeze in the state is recorded, runs colder again.

Texas is a serious freeze market because of its building stock rather than its ground frost. Houses here put supply piping in unconditioned attics and uninsulated exterior walls, because that is a rational thing to do in a climate with two cold weeks a year. When a February 2021 arrives, the buried service line is fine and the attic run splits. That is the exact inverse of the Minnesota failure pattern and it is why the same national advice serves both places badly.

So for a Texas homeowner the number to act on is the count of nights a year the air drops below 20°F, and the frost depth is close to irrelevant. The median Texas station sees about three such nights. San Antonio sees half a night. That is few enough that nothing is built for it and frequent enough that it happens.

Across all 476 Texas stations with published normals, the median first 32°F night falls around November 16 and the median station records 3.3 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 LIPSCOMB, where the median first freeze is October 15, to CORPUS CHRISTI NAS at January 8.

Texas has the widest internal spread of any state we cover: Lipscomb in the northern panhandle reaches its median first freeze on 15 October, and Corpus Christi Naval Air Station does not reach its until 8 January, almost three months later. The median station records about 3 nights a year below 20°F, against 104 in Minnesota. The state’s plumbing risk is concentrated into a handful of nights that arrive unpredictably, which is a harder problem to prepare for than a long, reliable winter.

Where these numbers come from

The Texas frost figure was researched against the body that publishes it, and it’s recorded with a confidence note of “local only, 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.
• City of Dallas Ordinance 23-0471, amendments to the 2021 IRC, Table R301.2 The Texas frost depth figure and basis.
• City of Lubbock Building Safety Department, local design criteria The Texas 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.