Frost Line Depth in San Diego County, California
- 1 verified code nearby
- Checked Oct 2026
No official local value
No official frost line depth is published for San Diego County.
Nearby official codes require 12 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: 28 nights a year at or below 32 °F (NOAA 1991–2020, Ramona Fire Dept, 7.7 mi).
Checked Oct 2026. Report a correction
Does San Diego County have an official frost line depth?
No adopted frost line depth found for San Diego County 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 County’s own number.
What frost line depth does San Diego County 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 County?
Drawn with the deepest nearby official value (12 in). Confirm San Diego County’s own depth before you dig.
House or garage footing in San Diego County: 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 County?
- J
- F
- M
- A
- M
- J
- J
- A
- S
- O
- N
- D
San Diego County never averages a low below freezing. 28 nights a year reach 32 °F or colder; Dec is coldest, with an average low of 36.6 °F.
NOAA 1991–2020 climate normals, Ramona Fire Dept station, 7.7 mi away, elevation 1,470 ft.
Monthly temperatures as a table
| °F | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Low | 37.9 | 39 | 41.3 | 43.3 | 48.7 | 52.1 | 57.1 | 59.2 | 55.3 | 49 | 43.1 | 36.6 |
| High | 67.5 | 67.7 | 68.8 | 73.2 | 77.2 | 84.5 | 90.3 | 92.3 | 90 | 82 | 74.2 | 66.9 |
San Diego County has more freezing nights than 191 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 County use?
One official code near San Diego County is verified.
| Place | Verified frost line | Distance |
|---|---|---|
| Mission Viejo | 12 in | 65 mi away |
How likely is the soil in San Diego County to heave?
USDA rates the sampled soil around San Diego County as 100% low for frost action (main soils: Fallbrook, Cieneba, Olivenhain).
USDA NRCS soil survey, 9 sample points within 2 mi. Higher frost action means more risk of heave; see frost heave.
San Diego County at a glance
- Frost line depth
- No official local value
- Population (2023 est.)
- 3,269,973
- Mean annual temperature
- 62.4 °F
- ZIP codes (116)
- 91901 · 91902 · 91905 · 91906 · 91910 · 91911 · 91913 · 91914 · 91915 · 91916 · 91917 · 91931 · 91932 · 91934 · 91935 · 91941 · 91942 · 91945 · 91948 · 91950 · 91962 · 91963 · 91977 · 91978 · 91980 · 92003 · 92004 · 92007 · 92008 · 92009 · 92010 · 92011 · 92014 · 92019 · 92020 · 92021 · 92024 · 92025 · 92026 · 92027 · 92028 · 92029 · 92036 · 92037 · 92040 · 92054 · 92055 · 92056 · 92057 · 92058 · 92059 · 92060 · 92061 · 92064 · 92065 · 92066 · 92067 · 92069 · 92070 · 92071 · 92075 · 92078 · 92081 · 92082 · 92083 · 92084 · 92086 · 92091 · 92092 · 92093 · 92096 · 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 · 92135 · 92136 · 92139 · 92140 · 92145 · 92147 · 92154 · 92155 · 92161 · 92173 · 92179 · 92182 · 92562 · 92672