Frost Line Depth in Coconino County, AZ: Flagstaff Requires 30 in

No official local value

No official frost line depth is published for Coconino County.

Nearby official codes require 30 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: 133 nights a year at or below 32 °F (NOAA 1991–2020, Grand Canyon E Entrance, 14.6 mi).

Checked Oct 2026. Report a correction

Footings Deck Water line Fence post

30 in1 verified code within 45 mi
133nights a year at or below 32 °F
77%of nearby soil rated “moderate” for frost action (USDA)

Does Coconino County have an official frost line depth?

No adopted frost line depth found for Coconino County in its official documents (checked Oct 2026). The nearest official values, from codes we verified, are 30 in. Use the deepest of them until the building department confirms Coconino County’s own number.

What frost line depth does Coconino County use for footings under Table R301.2(1)? Is it 30 in, like Flagstaff?

Call 811 at least a few working days before you dig, so buried lines are marked.
Confirm the frost line depth with the Coconino County building department.
Ask whether your project needs a permit (decks, larger sheds and footings usually do).
Dig below 30 in (the deepest nearby 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 Coconino County?

Drawn with the deepest nearby official value (30 in). Confirm Coconino County’s own depth before you dig.

House or garage footing Deck footing Water service line Fence post

House or garage footing in Coconino County: dig at least 30 in (76 cm). Below the frost line and at least 12 in deep (IRC R403.1.4).

Using the nearby official value of 30 in until Coconino County confirms its own
Project	Depth	Rule
House or garage footing	30 in	Below the frost line and at least 12 in deep (IRC R403.1.4)
Deck footing (attached)	30 in	Below the frost line and at least 12 in deep (IRC R507.3)
Water service line	36 in	6 in below the frost line and at least 12 in deep (IRC P2603.5)
Fence post bottom	30 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 Coconino County?

Average lows are at or below freezing from Nov to Mar. 133 nights a year reach 32 °F or colder; Dec is coldest, with an average low of 22.9 °F.

NOAA 1991–2020 climate normals, Grand Canyon E Entrance station, 14.6 mi away, elevation 7,480 ft.

Monthly temperatures as a table

°F	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Low	23.7	25.1	29.5	34.6	42.2	54.5	58.8	57.2	50.5	40.5	30.4	22.9
High	40.8	43.2	51	58.3	67.4	80.1	84.2	80.6	74.6	62.8	50.6	40.7

Coconino County has more freezing nights than 32 of the 35 other Arizona places we track. The Arizona median is 12. Coldest: Flagstaff; mildest: Yuma.

What frost line depth do towns near Coconino County use?

One official code near Coconino County is verified.

Official frost line depths near Coconino County
Place	Verified frost line	Distance
Flagstaff	30 in	45 mi away

How likely is the soil in Coconino County to heave?

Low 23%Moderate 77%

USDA rates the sampled soil around Coconino County as 23% low, 77% moderate for frost action (main soils: Atarque, Moquistation, Pocomate).

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

Coconino County at a glance

Frost line depth: No official local value
Population (2023 est.): 144,472
Mean annual temperature: 50.2 °F
ZIP codes (31): 85931 · 86001 · 86003 · 86004 · 86005 · 86011 · 86015 · 86016 · 86017 · 86018 · 86020 · 86022 · 86023 · 86024 · 86030 · 86035 · 86036 · 86038 · 86040 · 86044 · 86045 · 86046 · 86047 · 86052 · 86053 · 86054 · 86320 · 86336 · 86337 · 86434 · 86435