Frost Line Depth in Yellowstone County, Montana
- 1 verified code nearby
- Checked Oct 2026
No official local value
No official frost line depth is published for Yellowstone County.
Nearby official codes require 36 in (1 verified code).
Source and how we checked
We searched this place’s own code and website and found no published frost line depth.
Climate: 182 nights a year at or below 32 °F (NOAA 1991–2020, Huntley Exp Stn, 1.8 mi).
Checked Oct 2026. Report a correction
Does Yellowstone County have an official frost line depth?
No adopted frost line depth found for Yellowstone County in its official documents (checked Oct 2026). The nearest official values, from codes we verified, are 36 in. Use the deepest of them until the building department confirms Yellowstone County’s own number.
What frost line depth does Yellowstone County use for footings under Table R301.2(1)? Is it 36 in, like Billings?
How deep do footings, decks and water lines need to be in Yellowstone County?
Drawn with the deepest nearby official value (36 in). Confirm Yellowstone County’s own depth before you dig.
House or garage footing in Yellowstone County: dig at least 36 in (91 cm). Below the frost line and at least 12 in deep (IRC R403.1.4).
| Project | Depth | Rule |
|---|---|---|
| House or garage footing | 36 in | Below the frost line and at least 12 in deep (IRC R403.1.4) |
| Deck footing (attached) | 36 in | Below the frost line and at least 12 in deep (IRC R507.3) |
| Water service line | 42 in | 6 in below the frost line and at least 12 in deep (IRC P2603.5) |
| Fence post bottom | 36 in | No code rule; common practice is below the frost line |
Work out posts, concrete and footing sizes with the fence post depth calculator or the deck footing calculator.
How cold does it get in Yellowstone County?
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Average lows are at or below freezing from Oct to Apr. 182 nights a year reach 32 °F or colder; Jan is coldest, with an average low of 11.8 °F.
NOAA 1991–2020 climate normals, Huntley Exp Stn station, 1.8 mi away, elevation 3,034 ft.
Monthly temperatures as a table
| °F | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Low | 11.8 | 14.3 | 22.1 | 31.9 | 41.4 | 49.5 | 54.9 | 52.5 | 43.2 | 31.1 | 21 | 12.9 |
| High | 34.9 | 39.2 | 49.8 | 58.5 | 67.5 | 77.1 | 87.1 | 86.1 | 75.3 | 60.3 | 46.7 | 36.4 |
Yellowstone County has more freezing nights than 7 of the 7 other Montana places we track. The Montana median is 167. Coldest: Yellowstone County; mildest: Great Falls.
What frost line depth do towns near Yellowstone County use?
One official code near Yellowstone County is verified.
| Place | Verified frost line | Distance |
|---|---|---|
| Billings | 36 in | 17 mi away |
How likely is the soil in Yellowstone County to heave?
USDA rates the sampled soil around Yellowstone County as 55% low, 44% moderate, 1% high for frost action (main soils: Haverson, Vananda, Lohmiller).
USDA NRCS soil survey, 9 sample points within 2 mi. Higher frost action means more risk of heave; see frost heave.
Yellowstone County at a glance
- Frost line depth
- No official local value
- Population (2023 est.)
- 170,843
- Mean annual temperature
- 46.1 °F
- ZIP codes (16)
- 59002 · 59006 · 59015 · 59024 · 59037 · 59041 · 59044 · 59057 · 59063 · 59064 · 59079 · 59088 · 59101 · 59102 · 59105 · 59106