Last spring frost
Feb 12
Frost Dates for Jamul, CA
First fall frost
Dec 24
Growing season
317 days
Hardiness zone
10a
In an average year around Jamul, CA, the last spring frost (32°F) is about Feb 12 and the first fall frost is about Dec 24, giving roughly a 317-day growing season. To be safe most years, wait until Dec 29 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) | Apr 16 | Mar 17 | Feb 15 |
| Freeze (32°F) | Mar 20 | Feb 12 | Dec 29 |
| Hard (28°F) | Feb 23 | Jan 22 | Dec 12 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 16 | Apr 7 | Mar 31 | Mar 24 | Mar 17 | Mar 11 | Mar 3 | Feb 25 | Feb 15 |
| 32°F | Mar 20 | Mar 4 | Feb 26 | Feb 19 | Feb 12 | Feb 4 | Jan 27 | Jan 10 | Dec 29 |
| 28°F | Feb 23 | Feb 12 | Feb 4 | Jan 29 | Jan 22 | Jan 8 | Dec 31 | Dec 22 | Dec 12 |
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 15 | Dec 7 | Dec 23 |
| Freeze (32°F) | Dec 2 | Dec 24 | Feb 3 |
| Hard (28°F) | Dec 10 | Jan 4 | Feb 20 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Nov 15 | Nov 24 | Nov 29 | Dec 2 | Dec 7 | Dec 10 | Dec 13 | Dec 17 | Dec 23 |
| 32°F | Dec 2 | Dec 10 | Dec 14 | Dec 19 | Dec 24 | Dec 28 | Jan 1 | Jan 19 | Feb 3 |
| 28°F | Dec 10 | Dec 15 | Dec 25 | Dec 31 | Jan 4 | Jan 15 | Jan 27 | Feb 6 | Feb 20 |
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: Alpine, Ca, about 13.5 miles away@if(!empty($station['elevation_ft'])), at 1,695 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 Jamul, CA?
On average, the last spring frost (32°F) around Jamul, CA is about Feb 12. In cooler years it can run later, so for a safer bet many gardeners wait until Dec 29.
When is the first frost in the fall?
The first fall frost around Jamul, CA typically arrives about Dec 24. 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 Feb 12 on average, or Dec 29 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 317 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 91917 Planting calendar → California frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026