Frost Line Depth in Cascade County, MT: Montana Codes Range 36

No official local value

No official frost line depth is published for Cascade County.

No verified code nearby; verified Montana codes range 36–42 in.

Source and how we checked

We searched this place’s own code and website and found no published frost line depth.

Climate: 157 nights a year at or below 32 °F (NOAA 1991–2020, Great Falls Wfo, 10.1 mi).

Checked Oct 2026. Report a correction

Footings Deck Water line Fence post

36–42 inrange of verified Montana codes
157nights a year at or below 32 °F
77%of nearby soil rated “moderate” for frost action (USDA)

Does Cascade County have an official frost line depth?

No adopted frost line depth found for Cascade County in its official documents (checked Oct 2026). No verified code lies near Cascade County; the Montana codes we verified range from 36 to 42 in. Ask the building department for Cascade County’s own number before you dig.

What frost line depth does Cascade County use for footings under Table R301.2(1)?

Call 811 at least a few working days before you dig, so buried lines are marked.
Confirm the frost line depth with the Cascade County building department.
Ask whether your project needs a permit (decks, larger sheds and footings usually do).
Dig below 42 in (the deepest verified state value) unless the building department tells you otherwise.
Book the footing inspection before you pour concrete.

How deep do footings, decks and water lines need to be in Cascade County?

Drawn with the deepest Montana official value (42 in). Confirm Cascade County’s own depth before you dig.

House or garage footing Deck footing Water service line Fence post

House or garage footing in Cascade County: dig at least 42 in (107 cm). Below the frost line and at least 12 in deep (IRC R403.1.4).

Using the nearby official value of 42 in until Cascade County confirms its own
Project	Depth	Rule
House or garage footing	42 in	Below the frost line and at least 12 in deep (IRC R403.1.4)
Deck footing (attached)	42 in	Below the frost line and at least 12 in deep (IRC R507.3)
Water service line	48 in	6 in below the frost line and at least 12 in deep (IRC P2603.5)
Fence post bottom	42 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 Cascade County?

Average lows are at or below freezing from Nov to Apr. 157 nights a year reach 32 °F or colder; Jan is coldest, with an average low of 16 °F.

NOAA 1991–2020 climate normals, Great Falls Wfo station, 10.1 mi away, elevation 3,705 ft.

Monthly temperatures as a table

°F	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Low	16	16.8	23.7	31.6	40.3	47.7	53.7	52.3	44.9	34.5	25.3	17.8
High	35.4	36.7	45.8	54.2	64.1	72.2	83.2	81.8	70.7	56.6	43.5	35.5

Cascade County has fewer freezing nights than 6 of the 7 other Montana places we track. The Montana median is 167. Coldest: Yellowstone County; mildest: Great Falls.

How likely is the soil in Cascade County to heave?

Low 23%Moderate 77%

USDA rates the sampled soil around Cascade County as 23% low, 77% moderate for frost action (main soils: Bitton, Roy, Absarokee).

USDA NRCS soil survey, 9 sample points within 2 mi. Higher frost action means more risk of heave; see frost heave.

Cascade County at a glance

Frost line depth: No official local value
Population (2023 est.): 84,900
Mean annual temperature: 45.2 °F
ZIP codes (18): 59401 · 59404 · 59405 · 59412 · 59414 · 59421 · 59436 · 59440 · 59443 · 59463 · 59465 · 59468 · 59472 · 59477 · 59480 · 59483 · 59485 · 59487