Frost Dates for Foster City, CA
In Foster City, CA, the average last spring frost is around Jan 17 and the average first fall frost around Dec 12, for a growing season of about 333 days. For frost-tender plants, wait until Feb 16, when the chance of frost drops to 10%.
Based on NOAA 1991–2020 records from the Redwood City, CA weather station, 6 miles away, elevation 31 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% | Feb 16 | Nov 24 |
| 20% | Feb 5 | Dec 1 |
| 30% | Jan 31 | Dec 4 |
| 40% | Jan 25 | Dec 8 |
| 50% | Jan 17 | Dec 12 |
| 60% | Jan 10 | Dec 17 |
| 70% | Jan 3 | Dec 23 |
| 80% | Dec 29 | Jan 1 |
| 90% | Dec 20 | Jan 14 |
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) | Feb 25 | Nov 25 |
| Frost / freeze (32°F) | Jan 17 | Dec 12 |
| Hard freeze (28°F) | Dec 31 | Dec 26 |
Planting calendar for Foster City
Transplant Jan 24 – Feb 7
Transplant Jan 31 – Feb 14
Transplant Jan 31 – Feb 14
Transplant Jan 24 – Feb 7
Sow or transplant Jan 24 – Feb 7
Sow or transplant Jan 24 – Feb 7
Sow or transplant Jan 31 – Feb 14
Sow or transplant Dec 20 – Jan 3
Fall sowing Oct 17 – Nov 14
Fall sowing Oct 17 – Nov 7
Fall sowing Oct 3 – Oct 17
Sow or transplant Dec 20 – Jan 3
Fall sowing Oct 3 – Oct 31
Transplant Jan 3 – Jan 17
Fall sowing Sep 19 – Oct 3
Transplant Dec 27 – Jan 10
Fall sowing Sep 19 – Oct 3
Fall sowing Sep 19 – Oct 3
Fall sowing Oct 31 – Nov 21
Fall sowing Oct 3 – Oct 17
Plant Dec 20 – Jan 3
Based on the average last frost (Jan 17) and first frost (Dec 12). The dashed lines mark those dates. Seed packets list days to maturity; adjust for your varieties.