Florida fills in the climatic design table for the whole state and enters NA for frost line depth, so no frost depth applies anywhere in Florida and the code deletes the usual instruction for a local jurisdiction to fill the column in.
Florida's code carries the frost line depth row and enters NA in it.
Table R301.2(1). Change to read as shown: TABLE R301.2(1) CLIMATIC AND GEOGRAPHIC DESIGN CRITERIA ... SUBJECT TO DAMAGE FROM ... Frost line depth b ... NA ... b. Reserved.Florida Supplement to the 2015 IRC, ICC edit version, Florida Building Commission, read September 22, 2026. Read it at the source
The air freezing index is the quantity the frost provisions of the model codes are written on: add up how far each day’s mean temperature fell below freezing over a winter, in degree days, and take the deepest run the winter managed. It measures how much cold the ground had to absorb, which is why it is the honest way to set one place beside another. Tallahassee is the coldest of the 3 cities on the record in Florida.
2degree days
average freezing index a winter
Tallahassee Intl AP
| City | State | Freezing index | Once a century | Nights below freezing |
|---|---|---|---|---|
| Tallahassee | Florida | 2 | 16 | 29 |
| Miami | Florida | 0 | No freezing winter on record | 0 |
| Orlando | Florida | 0 | No freezing winter on record | 2 |
Computed from NOAA National Centers for Environmental Information, Global Historical Climatology Network daily temperature records for each station, from 1951 onward. These are measurements of winter, not depths.
Only a handful of states answer with one number for the whole state, and they are the only codes that can be set beside each other directly. Ranked by the freezing index at their own reference cities, with Florida marked at 1 degree days for comparison against what those codes settled on:
Left to right, the mildest winters to the hardest. The figure on the right is what that state wrote into its code.
The nearest by winter are North Carolina at 12 inches, Massachusetts at 4 feet and Connecticut at 42 inches. That is a reading of other states’ codes rather than a depth for an address in Florida: soil, drainage, snow cover and local amendments all move the figure, and the building department issuing the permit is the office whose number binds.
Florida code read September 22, 2026 from Florida Supplement to the 2015 IRC, ICC edit version, Florida Building Commission. Codes are amended and a local amendment can be deeper than the state figure, so the building department issuing the permit has the number that binds. Every state is on the frost line depth hub.