Frost Dates for Hercules, CA
In Hercules, CA, the average last spring frost is around Jan 17 and the average first fall frost around Dec 27, for a growing season of about 346 days. For frost-tender plants, wait until Mar 4, when the chance of frost drops to 10%.
Based on NOAA 1991–2020 records from the Vallejo, CA weather station, 8 miles away, elevation 341 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% | Mar 4 | Dec 4 |
| 20% | Feb 18 | Dec 11 |
| 30% | Feb 2 | Dec 17 |
| 40% | Jan 25 | Dec 21 |
| 50% | Jan 17 | Dec 27 |
| 60% | Jan 11 | Jan 1 |
| 70% | Jan 5 | Jan 7 |
| 80% | Dec 31 | Jan 16 |
| 90% | Dec 23 | Feb 4 |
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) | Mar 4 | Dec 7 |
| Frost / freeze (32°F) | Jan 17 | Dec 27 |
| Hard freeze (28°F) | Jan 5 | Jan 2 |
Planting calendar for Hercules
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 Nov 1 – Nov 29
Fall sowing Nov 1 – Nov 22
Fall sowing Oct 18 – Nov 1
Sow or transplant Dec 20 – Jan 3
Fall sowing Oct 18 – Nov 15
Transplant Jan 3 – Jan 17
Fall sowing Oct 4 – Oct 18
Transplant Dec 27 – Jan 10
Fall sowing Oct 4 – Oct 18
Fall sowing Oct 4 – Oct 18
Fall sowing Nov 15 – Dec 6
Fall sowing Oct 18 – Nov 1
Plant Dec 20 – Jan 3
Based on the average last frost (Jan 17) and first frost (Dec 27). The dashed lines mark those dates. Seed packets list days to maturity; adjust for your varieties.