Frost Dates for South San Francisco, CA
In South San Francisco, CA, the average last spring frost is around Dec 29 and the average first fall frost around Dec 26, for a growing season of about 365 days. For frost-tender plants, wait until Jan 13, when the chance of frost drops to 10%.
Based on NOAA 1991–2020 records from the San Francisco Intl. Airport, CA weather station, 3 miles away, elevation 8 ft. Frost can come earlier in low spots and valleys and later near cities and large lakes.
Frost probability by date
Chance of a 32°F frost after the spring date, or before the fall date.
| Chance | Last spring frost | First fall frost |
|---|---|---|
| 10% | Jan 13 | Dec 11 |
| 20% | Jan 7 | Dec 17 |
| 30% | Jan 3 | Dec 21 |
| 40% | Dec 31 | Dec 24 |
| 50% | Dec 29 | Dec 26 |
| 60% | Dec 26 | Dec 30 |
| 70% | Dec 23 | Jan 1 |
| 80% | Dec 17 | Jan 6 |
| 90% | Dec 11 | Jan 13 |
Light frost vs. hard freeze
Average (50%) dates for each temperature. Tender plants are damaged at 36°F; most hardy crops survive until 28°F.
| Temperature | Last in spring | First in fall |
|---|---|---|
| Light frost (36°F) | Jan 8 | Dec 24 |
| Frost / freeze (32°F) | Dec 29 | Dec 26 |
| Hard freeze (28°F) | — | — |
Planting calendar for South San Francisco
Transplant Jan 5 – Jan 19
Transplant Jan 12 – Jan 26
Transplant Jan 12 – Jan 26
Transplant Jan 5 – Jan 19
Sow or transplant Jan 5 – Jan 19
Sow or transplant Jan 5 – Jan 19
Sow or transplant Jan 12 – Jan 26
Sow or transplant Dec 1 – Dec 15
Fall sowing Oct 31 – Nov 28
Fall sowing Oct 31 – Nov 21
Fall sowing Oct 17 – Oct 31
Sow or transplant Dec 1 – Dec 15
Fall sowing Oct 17 – Nov 14
Transplant Dec 15 – Dec 29
Fall sowing Oct 3 – Oct 17
Transplant Dec 8 – Dec 22
Fall sowing Oct 3 – Oct 17
Fall sowing Oct 3 – Oct 17
Fall sowing Nov 14 – Dec 5
Fall sowing Oct 17 – Oct 31
Plant Dec 1 – Dec 15
Based on the average last frost (Dec 29) and first frost (Dec 26). The dashed lines mark those dates. Seed packets list days to maturity; adjust for your varieties.