Frost Dates for San Mateo, CA
In San Mateo, 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, 5 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 San Mateo
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.