Mississippi adopts no statewide residential building code and publishes no frost line depth of its own, so a reader gets the number from the county or municipal building department that issues the permit.
Mississippi leaves the frost line depth to the local building department, which is where the number for an address comes from.
To the extent the International Building Code (IBC) and the International Residential Code (IRC) apply or impact application of the International Fire Code (IFC), the most recent and current version shall be utilized.Title 19, Part 7, Chapter 7: Rules and Regulations for the Mississippi Fire Prevention Code, Mississippi Insurance Department, Office of the State Fire Marshal, read September 23, 2026. Read it at the source
That makes the building department issuing the permit the office with the number, and it is a short call: the counter gives the depth for the address, and the same call settles whether a deck footing or a slab edge needs a footing inspection before the concrete goes in. What Mississippi does publish is below, and it is worth having in hand first.
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. Tupelo is the coldest of the 3 cities on the record in Mississippi.
34degree days
average freezing index a winter
Tupelo Rgnl AP
| City | State | Freezing index | Once a century | Nights below freezing |
|---|---|---|---|---|
| Tupelo | Mississippi | 34 | 122 | 61 |
| Jackson | Mississippi | 14 | 60 | 44 |
| Biloxi | Mississippi | 2 | 15 | 13 |
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 Mississippi marked at 17 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 Mississippi: soil, drainage, snow cover and local amendments all move the figure, and the building department issuing the permit is the office whose number binds.
Mississippi code read September 23, 2026 from Title 19, Part 7, Chapter 7: Rules and Regulations for the Mississippi Fire Prevention Code, Mississippi Insurance Department, Office of the State Fire Marshal. 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.