Frost dates for 94581Napa, CA
The average last spring frost in Napa is February 12 and the average first fall frost is December 4, giving a typical growing season of about 299 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Feb 12
- Average first fall frost
- Dec 4
- Growing season
- 299 days
Safer after Mar 13 (1-in-10 risk)
Possible by Nov 15 (1-in-10 risk)
First frost typically in 35 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) | Feb 26 · Mar 27 · Apr 19 | Oct 31 · Nov 17 · Dec 4 | 236 days | 100% |
| Frost / freeze (32°F) | Jan 3 · Feb 12 · Mar 13 | Nov 15 · Dec 4 · Jan 4 | 299 days | 98% |
| Hard freeze (28°F) | Dec 16 · Jan 11 · Feb 13 | Dec 1 · Dec 19 · Jan 23 | 348 days | 71% |
Planting calendar for Napa
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 12 – Mar 20 |
| Tomatoes | Transplant outdoors | Feb 28 – Aug 14 |
| Peppers | Start seeds indoors | Jan 12 – Feb 12 |
| Peppers | Transplant outdoors | Mar 14 – Apr 14 |
| Eggplant | Start seeds indoors | Jan 29 – Feb 27 |
| Eggplant | Transplant outdoors | Mar 14 – Apr 14 |
| Cucumbers | Sow outdoors | Mar 14 – Aug 24 |
| Summer squash | Sow outdoors | Feb 28 – Apr 14 |
| Winter squash & pumpkins | Sow outdoors | Mar 14 – Apr 14 |
| Snap beans | Sow outdoors | Feb 28 – Sep 16 |
| Sweet corn | Sow outdoors | Feb 28 – Aug 14 |
| Watermelon & cantaloupe | Sow outdoors | Mar 14 – Apr 14 |
| Okra | Sow outdoors | Mar 7 – Mar 30 |
| Peas | Sow outdoors (spring) | Jan 12 – Feb 27 |
| Potatoes | Plant outdoors (spring) | Jan 12 – Mar 14 |
| Onions | Start seeds indoors (spring) | Dec 1 – Dec 28 |
| Onions | Transplant outdoors (spring) | Jan 29 – Feb 27 |
| Broccoli | Start seeds indoors (spring) | Dec 25 – Jan 28 |
| Broccoli | Transplant outdoors (spring) | Jan 29 – Feb 27 |
| Broccoli | Start seeds indoors (fall) | Aug 4 – Aug 14 |
| Broccoli | Transplant outdoors (fall) | Sep 3 – Sep 14 |
| Cabbage | Start seeds indoors (spring) | Dec 15 – Jan 12 |
| Cabbage | Transplant outdoors (spring) | Jan 12 – Feb 12 |
| Cabbage | Start seeds indoors (fall) | Jul 25 – Aug 24 |
| Cabbage | Transplant outdoors (fall) | Aug 24 – Sep 24 |
| Leaf lettuce | Sow outdoors (spring) | Jan 12 – Mar 30 |
| Leaf lettuce | Sow outdoors (fall) | Aug 24 – Oct 10 |
| Spinach | Sow outdoors (spring) | Jan 5 – Feb 18 |
| Spinach | Sow outdoors (fall) | Sep 10 – Oct 15 |
| Radishes | Sow outdoors (spring) | Jan 12 – Mar 4 |
| Radishes | Sow outdoors (fall) | Aug 24 – Oct 25 |
| Kale | Sow outdoors (spring) | Jan 29 – Feb 18 |
| Kale | Sow outdoors (fall) | Aug 17 – Sep 24 |
| Carrots | Sow outdoors (spring) | Feb 12 – Mar 30 |
| Carrots | Sow outdoors (fall) | Jul 25 – Sep 9 |
| Garlic | Plant outdoors (fall) | Nov 24 – Dec 25 |
Where these dates come from
ZIP code 94581 is matched to the NOAA station Napa State Hospital, CA, 2.8 km away, at 35 ft elevation (15 ft higher than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Napa State Hospital, CA (used) | 35 ft | Feb 12 | Dec 4 |
| Napa Co Ap, CA | 14 ft | Mar 5 | Nov 21 |
| Sonoma, CA | 97 ft | Mar 2 | Nov 27 |
| Fairfield, CA | 40 ft | Jan 15 | Dec 14 |
Frost dates near Napa
- Napa, CA 94559 · last Feb 12, first Dec 4
- Yountville, CA 94599 · last Mar 2, first Nov 27
- Vineburg, CA 95487 · last Mar 2, first Nov 27
- American Canyon, CA 94503 · last Mar 5, first Nov 21
- Fairfield, CA 94534 · last Jan 15, first Dec 14
- Vallejo, CA 94589 · last Mar 5, first Nov 21
- Sonoma, CA 95476 · last Mar 2, first Nov 27
- Boyes Hot Springs, CA 95416 · last Mar 2, first Nov 27
Frequently asked questions
- When is the last frost in Napa, CA?
- For ZIP code 94581, the average last spring frost (32°F) is February 12, based on NOAA 1991-2020 climate normals for the Napa State Hospital, CA weather station. There is a 1-in-10 chance of a frost after March 13.
- When is the first frost in Napa, CA?
- The average first fall frost (32°F) is December 4. There is a 1-in-10 chance of frost by November 15, so tender plants are at risk from that point on.
- How long is the growing season in 94581?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 299 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.