Frost Line Depth in Palo Alto, California
- Palo Alto’s adopted code
- Checked Oct 2026
- Sources
Verified
5in
13 cm · 5 in
Set in the building code Palo Alto has adopted.
Footings still go at least 12 in (30 cm) below undisturbed ground (IRC R403.1.4).
Source and how we checked
Document: paloalto.gov
Climate: 14 nights a year at or below 32 °F (NOAA 1991–2020, Palo Alto, 3.3 mi).
Checked Oct 2026. Report a correction
How deep is the frost line in Palo Alto?
Palo Alto's building authority sets the frost line depth at 5 in (13 cm). Footings, piers and other permanent supports still go at least 12 in below undisturbed ground (IRC R403.1.4).
Who sets the frost line depth in Palo Alto?
California leaves the frost line depth to each city or county, and Palo Alto fills it in when it adopts the residential code. The value above comes from Palo Alto’s own document on paloalto.gov. See how California sets frost line depth.
How deep do footings, decks and water lines need to be in Palo Alto?
House or garage footing in Palo Alto: dig at least 12 in (30 cm). Below the frost line and at least 12 in deep (IRC R403.1.4).
| Project | Depth | Rule |
|---|---|---|
| House or garage footing | 12 in | Below the frost line and at least 12 in deep (IRC R403.1.4) |
| Deck footing (attached) | 12 in | Below the frost line and at least 12 in deep (IRC R507.3) |
| Water service line | 12 in | 6 in below the frost line and at least 12 in deep (IRC P2603.5) |
| Fence post bottom | 12 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 Palo Alto?
- J
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- D
Palo Alto never averages a low below freezing. 14 nights a year reach 32 °F or colder; Dec is coldest, with an average low of 38.6 °F.
NOAA 1991–2020 climate normals, Palo Alto station, 3.3 mi away, elevation 25 ft.
Monthly temperatures as a table
| °F | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Low | 39 | 41.3 | 43.6 | 45.3 | 49.5 | 52.7 | 55.7 | 55.3 | 53 | 48.4 | 42.5 | 38.6 |
| High | 57.8 | 60.7 | 65.5 | 69.6 | 73.3 | 78.5 | 79.4 | 78.7 | 79.6 | 74 | 63.7 | 57.6 |
Palo Alto has more freezing nights than 155 of the 208 other California places we track. The California median is 3. Coldest: El Dorado County; mildest: San Diego.
What frost line depth do towns near Palo Alto use?
5 official codes near Palo Alto are verified; each links to its document.
| Place | Verified frost line | Distance |
|---|---|---|
| Campbell | 12 in | 13 mi away |
| Dublin | 12 in | 26 mi away |
| Santa Cruz | 12 in | 30 mi away |
| Watsonville | 12 in | 39 mi away |
| Brentwood | 30 in | 44 mi away |
How likely is the soil in Palo Alto to heave?
USDA rates the sampled soil around Palo Alto as 100% none for frost action (main soils: Urban land, Diablo, Flaskan).
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 Palo Alto?
Palo Alto at a glance
- Frost line depth
- 5 in
- County
- Santa Clara County
- Population (2023 est.)
- 65,882
- Mean annual temperature
- 58.5 °F
- ZIP codes (9)
- 94022 · 94028 · 94043 · 94301 · 94303 · 94304 · 94305 · 94306 · 95033