Frost Line Depth in Kittitas County, Washington
- Kittitas County’s adopted code
- Checked Oct 2026
- Sources
Verified
24in
61 cm · 2 ft
Set in the building code Kittitas County has adopted.
Source and how we checked
Document: co.kittitas.wa.us
Climate: 139 nights a year at or below 32 °F (NOAA 1991–2020, Ellensburg Bowers Fld, 9.3 mi).
Checked Oct 2026. Report a correction
How deep is the frost line in Kittitas County?
Kittitas County's building authority sets the frost line depth at 24 in (61 cm). Footings, piers and other permanent supports must reach at least this depth (IRC R403.1.4.1).
Who sets the frost line depth in Kittitas County?
Washington leaves the frost line depth to each city or county, and Kittitas County fills it in when it adopts the residential code. The value above comes from Kittitas County’s own document on co.kittitas.wa.us. See how Washington sets frost line depth.
How deep do footings, decks and water lines need to be in Kittitas County?
House or garage footing in Kittitas County: dig at least 24 in (61 cm). Below the frost line and at least 12 in deep (IRC R403.1.4).
| 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 Kittitas County?
- J
- F
- M
- A
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- J
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- N
- D
Average lows are at or below freezing from Nov to Mar. 139 nights a year reach 32 °F or colder; Dec is coldest, with an average low of 23.8 °F.
NOAA 1991–2020 climate normals, Ellensburg Bowers Fld station, 9.3 mi away, elevation 1,766 ft.
Monthly temperatures as a table
| °F | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Low | 24.1 | 26.8 | 30.9 | 36.5 | 44.9 | 50.9 | 56.8 | 55.9 | 46.9 | 36.9 | 28.7 | 23.8 |
| High | 36.6 | 44.2 | 53.3 | 61.4 | 71 | 77.4 | 86.4 | 86.5 | 77.5 | 62.3 | 46.6 | 36.4 |
Kittitas County has more freezing nights than 44 of the 47 other Washington places we track. The Washington median is 54. Coldest: Chelan County; mildest: Lakewood.
What frost line depth do towns near Kittitas County use?
2 official codes near Kittitas County are verified; each links to its document.
| Place | Verified frost line | Distance |
|---|---|---|
| King County | 12 in | 60 mi away |
| Pierce County | 18 in | 70 mi away |
How likely is the soil in Kittitas County to heave?
USDA rates the sampled soil around Kittitas County as 23% low, 77% moderate for frost action (main soils: Weirman, Maxhill, Reelow).
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 Kittitas County?
Kittitas County at a glance
- Frost line depth
- 24 in
- Population (2023 est.)
- 45,508
- Mean annual temperature
- 50.1 °F
- ZIP codes (12)
- 98068 · 98828 · 98901 · 98922 · 98925 · 98926 · 98934 · 98940 · 98941 · 98943 · 98946 · 98950