Canyon County, ID Frost Line Depth: 24 in

Verified

24in

61 cm · 2 ft

Set in the building code Canyon County has adopted.

Source and how we checked

Document: canyoncounty.id.gov

Climate: 106 nights a year at or below 32 °F (NOAA 1991–2020, Deer Flat Dam, 3.9 mi).

Checked Oct 2026. Report a correction

Footings Deck Water line Fence post

2 of 2nearby verified codes use the same depth
106nights a year at or below 32 °F
95%of nearby soil rated “low” for frost action (USDA)

How deep is the frost line in Canyon County?

"{confirmed quote}". Footings, piers and other permanent supports must reach at least this depth (IRC R403.1.4.1).

Who sets the frost line depth in Canyon County?

Idaho leaves the frost line depth to each city or county, and Canyon County fills it in when it adopts the residential code. The value above comes from Canyon County’s own document on canyoncounty.id.gov. See how Idaho sets frost line depth.

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

House or garage footing Deck footing Water service line Fence post

House or garage footing in Canyon County: dig at least 24 in (61 cm). Below the frost line and at least 12 in deep (IRC R403.1.4).

Minimum depths in Canyon County with a 24 in frost line
Project	Depth	Rule
House or garage footing	24 in	Below the frost line and at least 12 in deep (IRC R403.1.4)
Deck footing (attached)	24 in	Below the frost line and at least 12 in deep (IRC R507.3)
Water service line	30 in	6 in below the frost line and at least 12 in deep (IRC P2603.5)
Fence post bottom	24 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 Canyon County?

Average lows are at or below freezing from Nov to Feb. 106 nights a year reach 32 °F or colder; Dec is coldest, with an average low of 24 °F.

NOAA 1991–2020 climate normals, Deer Flat Dam station, 3.9 mi away, elevation 2,510 ft.

Monthly temperatures as a table

°F	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Low	24.5	27.3	33.8	38.4	46	52.1	59.2	57	49	39.2	30.5	24
High	39.8	47.4	58.4	64.5	73.1	80.9	89.9	89.1	80	66.4	50.3	40.1

Canyon County has fewer freezing nights than 13 of the 13 other Idaho places we track. The Idaho median is 132. Coldest: Madison County; mildest: Canyon County.

What frost line depth do towns near Canyon County use?

2 official codes near Canyon County are verified; each links to its document.

Official frost line depths near Canyon County
Place	Verified frost line	Distance
Nampa	24 in	8 mi away
Meridian	24 in	15 mi away

How likely is the soil in Canyon County to heave?

Low 95%

USDA rates the sampled soil around Canyon County as 95% low, 5% moderate for frost action (main soils: Purdam, Power, Greenleaf).

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

How do you confirm the frost line before you dig in Canyon County?

Call 811 at least a few working days before you dig, so buried lines are marked.
Confirm the frost line depth with the Canyon County building department.
Ask whether your project needs a permit (decks, larger sheds and footings usually do).
Dig below 24 in unless the building department tells you otherwise.
Book the footing inspection before you pour concrete.

Canyon County at a glance

Frost line depth: 24 in
Population (2023 est.): 257,674
Mean annual temperature: 52.5 °F
ZIP codes (13): 83605 · 83607 · 83626 · 83634 · 83641 · 83644 · 83651 · 83656 · 83660 · 83669 · 83676 · 83686 · 83687