USDA Hardiness Zone 10b
Frost Dates for 92123 — San Diego, California
Averages from El Cajon, Ca US, the nearest reporting station, 12.1 miles away.
Plant tender crops after January 6, and expect the first autumn freeze around December 21. That leaves about 350 frost-free days.
- Last spring frost
- January 6
- First fall frost
- December 21
- Growing season
- 350 days
- Hardiness zone
- 10b
50% probability
50% probability
frost-free
35 to 40°F annual low
Planting calendar for 92123
| When | What to do |
|---|---|
| October 28 – November 11 | Start peppers and aubergines indoors They need eight to ten weeks under lights before they can go out. |
| November 11 – November 25 | Start tomatoes indoors Six to eight weeks gives a transplant big enough to set fruit early. |
| December 9 – December 23 | Sow peas, spinach, lettuce, radish outdoors These tolerate light frost and prefer to germinate in cool soil. |
| January 6 onward | Transplant tomatoes, peppers, basil, squash, cucumbers The average last freeze has passed — still watch the actual forecast. |
| by September 28 | Sow the autumn crop of carrots, beets and brassicas They need about twelve weeks to size up before growth stops. |
| by December 7 | Harvest tender crops, or be ready to cover them A first freeze two weeks early is well within normal variation. |
| December 21 onward | Plant garlic, mulch beds, lift tender bulbs Garlic wants a cold spell; bare soil loses structure over winter. |
What these dates mean
Wait until after January 6 to put tender plants — tomatoes, peppers, basil, squash — in the ground. That is the date by which half of years in San Diego, California are past their last freeze. Harvest before December 21, which leaves roughly 350 frost-free days.
ZIP 92123 sits in USDA hardiness zone 10b, meaning the average coldest night of the year falls between 35 to 40°F. Zone decides what survives the winter; frost dates decide when to plant each spring. They are different questions, and a plant can pass one and fail the other.
These are thirty-year NOAA averages for 1991–2020, not a forecast. Any individual year can frost two to three weeks either side of these dates, so check the actual forecast before planting out.