Utah adopts the 2021 International Residential Code statewide and writes its own table for ground snow load by city, but it publishes no matching frost depth table, so the frost line that governs your footing is the one your local building department has filled in.
Utah leaves the frost line depth to the local building department, which is where the number for an address comes from.
(19) In IRC, Figure R301.2 (3), is deleted and replaced with R301.2 (3) as follows: "TABLE R301.2 (3) GROUND SNOW LOADS FOR SELECTED LOCATIONS IN UTAH"Utah Code Section 15A-3-202, Amendments to Chapters 1 through 5 of IRC, Utah Legislature, read September 22, 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 Utah 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. Logan is the coldest of the 3 cities on the record in Utah.
759degree days
average freezing index a winter
Logan
| City | State | Freezing index | Once a century | Nights below freezing |
|---|---|---|---|---|
| Logan | Utah | 759 | 2,021 | 166 |
| Salt Lake City | Utah | 272 | 902 | 119 |
| St. George | Utah | 12 | 72 | 74 |
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 Utah marked at 348 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 Massachusetts at 4 feet, Connecticut at 42 inches and North Carolina at 12 inches. That is a reading of other states’ codes rather than a depth for an address in Utah: soil, drainage, snow cover and local amendments all move the figure, and the building department issuing the permit is the office whose number binds.
Utah code read September 22, 2026 from Utah Code Section 15A-3-202, Amendments to Chapters 1 through 5 of IRC, Utah Legislature. 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.