Frost dates for 94547Hercules, CA
The average last spring frost in Hercules is February 28 and the average first fall frost is November 22, giving a typical growing season of about 266 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Feb 28
- Average first fall frost
- Nov 22
- Growing season
- 266 days
Safer after Apr 5 (1-in-10 risk)
Possible by Nov 7 (1-in-10 risk)
First frost typically in 23 days
Frost risk by date
NOAA reports frost dates as probabilities. The middle date is the average (a 50% chance). For spring, the 10% date is a safer planting date: frost after it happens in about 1 year in 10. Light frost (36°F) can damage tender plants; a hard freeze (28°F) kills most annuals.
| Temperature | Last spring: 90% / 50% / 10% chance | First fall: 10% / 50% / 90% chance | Growing season (50%) | Years with at least one |
|---|---|---|---|---|
| Light frost (36°F) | Mar 15 · Apr 10 · May 3 | Oct 27 · Nov 7 · Nov 21 | 210 days | 100% |
| Frost / freeze (32°F) | Jan 29 · Feb 28 · Apr 5 | Nov 7 · Nov 22 · Dec 10 | 266 days | 100% |
| Hard freeze (28°F) | Dec 25 · Jan 23 · Feb 25 | Nov 20 · Dec 9 · Jan 6 | 323 days | 93% |
Planting calendar for Hercules
Planting windows from the University of Maryland Extension calendar, shifted to your average frost dates. Use them as a starting point and adjust for seed packet instructions and local conditions.
| Crop | Task | Window |
|---|---|---|
| Tomatoes | Start seeds indoors | Jan 28 – Apr 5 |
| Tomatoes | Transplant outdoors | Mar 16 – Aug 2 |
| Peppers | Start seeds indoors | Jan 28 – Feb 28 |
| Peppers | Transplant outdoors | Mar 30 – Apr 30 |
| Eggplant | Start seeds indoors | Feb 14 – Mar 15 |
| Eggplant | Transplant outdoors | Mar 30 – Apr 30 |
| Cucumbers | Sow outdoors | Mar 30 – Aug 12 |
| Summer squash | Sow outdoors | Mar 16 – Apr 30 |
| Winter squash & pumpkins | Sow outdoors | Mar 30 – Apr 30 |
| Snap beans | Sow outdoors | Mar 16 – Sep 4 |
| Sweet corn | Sow outdoors | Mar 16 – Aug 2 |
| Watermelon & cantaloupe | Sow outdoors | Mar 30 – Apr 30 |
| Okra | Sow outdoors | Mar 23 – Apr 15 |
| Peas | Sow outdoors (spring) | Jan 28 – Mar 15 |
| Potatoes | Plant outdoors (spring) | Jan 28 – Mar 30 |
| Onions | Start seeds indoors (spring) | Dec 17 – Jan 13 |
| Onions | Transplant outdoors (spring) | Feb 14 – Mar 15 |
| Broccoli | Start seeds indoors (spring) | Jan 10 – Feb 13 |
| Broccoli | Transplant outdoors (spring) | Feb 14 – Mar 15 |
| Broccoli | Start seeds indoors (fall) | Jul 23 – Aug 2 |
| Broccoli | Transplant outdoors (fall) | Aug 22 – Sep 2 |
| Cabbage | Start seeds indoors (spring) | Dec 31 – Jan 28 |
| Cabbage | Transplant outdoors (spring) | Jan 28 – Feb 28 |
| Cabbage | Start seeds indoors (fall) | Jul 13 – Aug 12 |
| Cabbage | Transplant outdoors (fall) | Aug 12 – Sep 12 |
| Leaf lettuce | Sow outdoors (spring) | Jan 28 – Apr 15 |
| Leaf lettuce | Sow outdoors (fall) | Aug 12 – Sep 28 |
| Spinach | Sow outdoors (spring) | Jan 21 – Mar 6 |
| Spinach | Sow outdoors (fall) | Aug 29 – Oct 3 |
| Radishes | Sow outdoors (spring) | Jan 28 – Mar 20 |
| Radishes | Sow outdoors (fall) | Aug 12 – Oct 13 |
| Kale | Sow outdoors (spring) | Feb 14 – Mar 6 |
| Kale | Sow outdoors (fall) | Aug 5 – Sep 12 |
| Carrots | Sow outdoors (spring) | Feb 28 – Apr 15 |
| Carrots | Sow outdoors (fall) | Jul 13 – Aug 28 |
| Garlic | Plant outdoors (fall) | Nov 12 – Dec 13 |
Where these dates come from
ZIP code 94547 is matched to the NOAA station Martinez Wtp, CA, 13.1 km away, at 40 ft elevation (39 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Martinez Wtp, CA (used) | 40 ft | Feb 28 | Nov 22 |
| Vallejo, CA | 341 ft | Jan 17 | Dec 27 |
| Richmond, CA | 20 ft | Jan 4 | Jan 2 |
| Berkeley, CA | 310 ft | Jan 3 | Jan 1 |
Frost dates near Hercules
- Pinole, CA 94564 · last Jan 4, first Jan 2
- Rodeo, CA 94572 · last Feb 28, first Nov 22
- El Sobrante, CA 94820 · last Jan 3, first Jan 1
- Crockett, CA 94525 · last Feb 28, first Nov 22
- San Pablo, CA 94806 · last Jan 4, first Jan 2
- Port Costa, CA 94569 · last Feb 28, first Nov 22
- Richmond, CA 94805 · last Jan 4, first Jan 2
- Vallejo, CA 94592 · last Mar 5, first Nov 21
Frequently asked questions
- When is the last frost in Hercules, CA?
- For ZIP code 94547, the average last spring frost (32°F) is February 28, based on NOAA 1991-2020 climate normals for the Martinez Wtp, CA weather station. There is a 1-in-10 chance of a frost after April 5.
- When is the first frost in Hercules, CA?
- The average first fall frost (32°F) is November 22. There is a 1-in-10 chance of frost by November 7, so tender plants are at risk from that point on.
- How long is the growing season in 94547?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 266 days long.
- Are these frost dates a forecast?
- No. They are 30-year averages and probabilities from NOAA weather station records. Use them to plan, then watch your local forecast before planting tender crops or leaving them uncovered.