Frost Line Depth in San Diego, California
- 1 verified code nearby
- Checked Oct 2026
No official local value
Frost rarely reaches the ground in San Diego.
Nearby official codes require 12 in (1 verified code).
Footings still go at least 12 in (30 cm) below undisturbed ground (IRC R403.1.4).
Source and how we checked
We searched this place’s own code and website and found no published frost line depth.
Climate: 0 nights a year at or below 32 °F (NOAA 1991–2020, San Diego Montgomery Fld, 0.2 mi).
Checked Oct 2026. Report a correction
Does San Diego have an official frost line depth?
No adopted frost line depth found for San Diego in its official documents (checked Oct 2026). The nearest official values, from codes we verified, are 12 in. Use the deepest of them until the building department confirms San Diego’s own number.
What frost line depth does San Diego use for footings under Table R301.2(1)? Is it 12 in, like Mission Viejo?
How deep do footings, decks and water lines need to be in San Diego?
Drawn with the deepest nearby official value (12 in). Confirm San Diego’s own depth before you dig.
House or garage footing in San Diego: 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 | 18 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 San Diego?
- J
- F
- M
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- J
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- D
San Diego never averages a low below freezing. 0 nights a year reach 32 °F or colder; Dec is coldest, with an average low of 45.3 °F.
NOAA 1991–2020 climate normals, San Diego Montgomery Fld station, 0.2 mi away, elevation 417 ft.
Monthly temperatures as a table
| °F | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Low | 46 | 46.9 | 49.6 | 52.4 | 56.6 | 60 | 64 | 65.3 | 63.6 | 57.8 | 50.1 | 45.3 |
| High | 67.3 | 67.3 | 68.5 | 70.7 | 72.1 | 74.7 | 79.8 | 82 | 81.4 | 77.8 | 72.7 | 67.3 |
San Diego has fewer freezing nights than 166 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 San Diego use?
One official code near San Diego is verified.
| Place | Verified frost line | Distance |
|---|---|---|
| Mission Viejo | 12 in | 63 mi away |
How likely is the soil in San Diego to heave?
USDA rates the sampled soil around San Diego as 100% low for frost action (main soils: Redding, Olivenhain, Chesterton).
USDA NRCS soil survey, 9 sample points within 2 mi. Higher frost action means more risk of heave; see frost heave.
San Diego at a glance
- Frost line depth
- No official local value
- County
- San Diego County
- Population (2023 est.)
- 1,388,320
- Mean annual temperature
- 64.1 °F
- ZIP codes (60)
- 91902 · 91911 · 91915 · 91932 · 91942 · 91945 · 91950 · 92014 · 92025 · 92027 · 92029 · 92037 · 92064 · 92065 · 92067 · 92071 · 92075 · 92092 · 92093 · 92101 · 92102 · 92103 · 92104 · 92105 · 92106 · 92107 · 92108 · 92109 · 92110 · 92111 · 92113 · 92114 · 92115 · 92116 · 92117 · 92118 · 92119 · 92120 · 92121 · 92122 · 92123 · 92124 · 92126 · 92127 · 92128 · 92129 · 92130 · 92131 · 92132 · 92134 · 92136 · 92139 · 92140 · 92145 · 92147 · 92154 · 92155 · 92161 · 92173 · 92182