Last spring frost
Jan 2
Frost Dates for San Marcos, CA
First fall frost
Dec 30
Growing season
365 days
Hardiness zone
10a
In an average year around San Marcos, CA, the last spring frost (32°F) is about Jan 2 and the first fall frost is about Dec 30, giving roughly a 365-day growing season. To be safe most years, wait until Dec 14 before setting out tender plants.
Last spring frost
Dates the last frost of spring typically ends. Plant tender crops after the risk has passed for your comfort level.
| Frost intensity | Early (10%) | Average (50%) | Late (90%) |
|---|---|---|---|
| Light (36°F) | Mar 1 | Jan 31 | Dec 29 |
| Freeze (32°F) | Feb 4 | Jan 2 | Dec 14 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Mar 1 | Feb 21 | Feb 13 | Feb 5 | Jan 31 | Jan 21 | Jan 13 | Jan 5 | Dec 29 |
| 32°F | Feb 4 | Jan 25 | Jan 14 | Jan 7 | Jan 2 | Dec 31 | Dec 28 | Dec 22 | Dec 14 |
First fall frost
Dates the first frost of fall typically arrives. Count back by a crop's days-to-maturity to know your planting cutoff.
| Frost intensity | Early (10%) | Average (50%) | Late (90%) |
|---|---|---|---|
| Light (36°F) | Nov 27 | Dec 18 | Jan 19 |
| Freeze (32°F) | Dec 8 | Dec 30 | Jan 29 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Nov 27 | Dec 4 | Dec 10 | Dec 14 | Dec 18 | Dec 22 | Dec 26 | Jan 1 | Jan 19 |
| 32°F | Dec 8 | Dec 15 | Dec 23 | Dec 27 | Dec 30 | Jan 1 | Jan 7 | Jan 14 | Jan 29 |
Growing season is measured at 32°F with about 50% probability. Hardiness zone from the 2023 USDA map; frost normals from NOAA 1991-2020.
Where this data comes from
@endif These dates are computed from the nearest official weather station with long-term records: Escondido #2, Ca, about 5.3 miles away@if(!empty($station['elevation_ft'])), at 600 ft elevation. The further the station and the greater the elevation difference from your yard, the more your local frost timing can vary.
How we calculate these dates
Frost and freeze dates come from the NOAA 1991–2020 U.S. Climate Normals, the National Oceanic and Atmospheric Administration's 30-year averages for each weather station. A date shown at the 50% level is the median: in half of years the frost falls on or before it. The 10% and 90% columns show the early and late ends of the range, so you can plant on the odds you're comfortable with. These are long-term averages, not a forecast for this year - always check your local outlook before planting.
Source: NOAA National Centers for Environmental Information, 1991–2020 Climate Normals (public domain). Harman is not affiliated with or endorsed by NOAA.
Frequently asked questions
When is the last frost in San Marcos, CA?
On average, the last spring frost (32°F) around San Marcos, CA is about Jan 2. In cooler years it can run later, so for a safer bet many gardeners wait until Dec 14.
When is the first frost in the fall?
The first fall frost around San Marcos, CA typically arrives about Dec 30. Count back by a crop's days to maturity to find the latest date you can plant it.
When can I plant tomatoes and other tender crops?
Tender crops like tomatoes, peppers and basil are damaged by frost, so wait until the last spring frost has passed - around Jan 2 on average, or Dec 14 to be safe most years.
How long is the growing season here?
The frost-free growing season (between the last spring and first fall 32°F frost) is about 365 days in a typical year.
Are these dates a forecast for this year?
No. They are 30-year averages from the NOAA 1991–2020 Climate Normals, not a prediction for the current year. Use them for planning and always check your local weather forecast before planting or protecting crops.
Local weather for 92078 Planting calendar → California frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026