San Ysidro, CA frost dates
Frost is light and occasional here — typically a few cold nights around midwinter (about 1 a year). Cover tender plants when frost is forecast.
How San Ysidro compares
- In a typical year, frost nights in San Ysidro fall between January 1 and January 10. In 1 year in 10 the first frost comes as early as December 8, or the last frost as late as February 16.
- Compared with Escondido, CA, 50 km away, the last frost here is 8 days later than there.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | December 12 |
| 50% (median) | January 10 |
| 10% (safe for tender plants) | February 16 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | December 8 |
| 50% (median) | January 1 |
| 90% (late) | February 11 |
Frost here means 32°F (0°C). A median date means half of years have their last frost earlier and half later.
Gardening where frost is rare
San Ysidro, CA only freezes on a few winter nights, so the usual "plant after the last frost" rule doesn't apply. Heat and rainfall decide the seasons instead:
- Cool-season crops (lettuce, broccoli, peas, carrots) grow best from fall through late winter.
- Warm-season crops (tomatoes, peppers, beans, squash) do best planted in late winter to spring, and again in late summer for a fall crop — midsummer heat can stop tomatoes setting fruit.
- Heat lovers (okra, sweet potatoes, melons) can be planted through spring and early summer.
About these dates
Based on 1991–2020 NOAA climate normals for the Borrego Desert Park, CA weather station, 15 km away (elevation 810 ft (247 m)).
Frost dates near San Ysidro
- Ranchita Jan 10 · Jan 1
- Warner Springs Apr 18 · Oct 26
- Santa Ysabel Apr 18 · Oct 26
- Borrego Springs Jan 10 · Jan 1
- Julian Mar 27 · Dec 1
- Palomar Mountain Apr 29 · Nov 18
- Aguanga Apr 29 · Nov 18
- Ramona Mar 4 · Dec 4
- Pauma Valley Feb 19 · Dec 1
- Anza May 16 · Oct 24
Frequently asked questions
When is the last frost in San Ysidro, CA?
The median last spring frost in San Ysidro, CA is January 10. There is still about a 10% chance of frost after February 16, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in San Ysidro, CA?
The median first fall frost is January 1, with about a 10% chance of frost before December 8.
How long is the growing season in San Ysidro, CA?
About 356 days between the median last spring frost and first fall frost.
What planting zone is San Ysidro, CA?
San Ysidro, CA is in USDA hardiness zone 10b.