Napa, California: planting zone & frost dates
Napa is in USDA plant hardiness zone 9b, where the average coldest winter night reaches 25 to 30°F (-3.9 to -1.1°C). The typical last spring frost is around Feb 27 and the first fall frost around Nov 28.
Frost dates
| Probability | Last spring frost (32°F) | First fall frost (32°F) |
|---|---|---|
| Safer (10% risk) | Mar 13 | Nov 15 |
| Typical planning date (30% risk) | Feb 27 | Nov 28 |
| Median (50%) | Feb 12 | Dec 4 |
How to read this: after the spring "10% risk" date, a 32°F frost happens in only about 1 year in 10. In fall, the "10% risk" date is the early end — a frost before it happens about 1 year in 10.
Frost data comes from NOAA station NAPA STATE HOSPITAL, CA (USC00046074), 2.4 mi (3.9 km) from the city center and 13 ft lower than the city center (-4 m). Record used for the 1991–2020 normals: 28 years.
Why your yard may differ from the station: microclimates.
Hardiness zone across Napa
All 2 ZIP codes covering Napa are in zone 9b.
Vegetable planting calendar for Napa
Dates are counted from the 30%-risk frost dates above (last frost Feb 27, first frost Nov 28). Shift a week later in cold spots or low-lying ground.
| Crop | Start indoors | Transplant / plant out | Direct sow | Fall crop sow/plant |
|---|---|---|---|---|
| Tomato | Jan 2 – Jan 16 | Mar 6 – Mar 20 | — | — |
| Pepper | Dec 19 – Jan 2 | Mar 13 – Mar 27 | — | — |
| Lettuce Mild winters: fall and winter plantings are usually more reliable than spring. | Jan 16 – Jan 30 | Feb 13 – Mar 6 | Jan 30 – Mar 13 | Sep 19 – Oct 17 |
| Green Beans | — | — | Mar 6 – Apr 10 | Sep 5 – Sep 19 |
| Sweet Corn | — | — | Mar 6 – Apr 3 | — |
| Zucchini & Summer Squash | Jan 30 – Feb 6 | Mar 6 – Mar 20 | Mar 6 – Mar 27 | Sep 5 – Sep 19 |
| Cucumber | Jan 30 – Feb 6 | Mar 13 – Mar 20 | Mar 6 – Mar 27 | Sep 5 – Sep 19 |
| Carrot Mild winters: fall and winter plantings are usually more reliable than spring. | — | — | Feb 6 – Mar 13 | Sep 5 – Sep 19 |
| Onion Mild winters: fall and winter plantings are usually more reliable than spring. | Dec 5 – Dec 19 | Jan 30 – Feb 13 | — | — |
| Potato Mild winters: fall and winter plantings are usually more reliable than spring. | — | Jan 30 – Feb 20 | — | — |
| Basil | Jan 16 – Jan 30 | Mar 13 – Mar 27 | Mar 13 – Apr 3 | — |
| Spinach Mild winters: fall and winter plantings are usually more reliable than spring. | — | — | Jan 16 – Feb 13 | Oct 3 – Oct 31 |
| Kale Mild winters: fall and winter plantings are usually more reliable than spring. | Jan 2 – Jan 16 | Jan 30 – Feb 20 | Jan 30 – Feb 20 | Sep 19 – Oct 17 |
| Broccoli Mild winters: fall and winter plantings are usually more reliable than spring. | Jan 2 – Jan 16 | Feb 13 – Mar 6 | — | Sep 5 – Sep 19 |
| Peas Mild winters: fall and winter plantings are usually more reliable than spring. | — | — | Jan 16 – Feb 6 | Sep 19 – Oct 3 |
| Eggplant | Dec 19 – Jan 2 | Mar 13 – Mar 27 | — | — |
| Cabbage Mild winters: fall and winter plantings are usually more reliable than spring. | Jan 2 – Jan 16 | Jan 30 – Feb 13 | — | Sep 5 – Sep 19 |
| Radish Mild winters: fall and winter plantings are usually more reliable than spring. | — | — | Jan 23 – Mar 13 | Oct 17 – Nov 14 |
| Strawberry | — | Jan 30 – Feb 20 | — | — |
| Beets Mild winters: fall and winter plantings are usually more reliable than spring. | — | — | Feb 6 – Mar 20 | Sep 19 – Oct 3 |
Nearby cities in California
- Vallejo — zone 9b, last frost Mar 25, first frost Nov 12
- Fairfield — zone 9b, last frost Jan 28, first frost Dec 7
- Vacaville — zone 9b, last frost Mar 3, first frost Nov 21
- Richmond — zone 10a, last frost Jan 14, first frost Dec 27
- Santa Rosa — zone 9a, last frost Mar 7, first frost Nov 21
- Berkeley — zone 10a, last frost Jan 12, first frost Dec 25
More: all California cities · other zone 9b cities: Houston, TX, Phoenix, AZ, Jacksonville, FL, San Jose, CA, Fresno, CA, Sacramento, CA, Mesa, AZ, Bakersfield, CA
Napa gardening questions
When is the last frost in Napa, CA?
Plan around Feb 27. At NOAA's Napa State Hospital, CA station, 2.4 mi from the city center, there is a 30% chance of a 32°F frost after that date. Half of springs have their last frost by Feb 12, and after Mar 13 the risk drops to about 1 in 10. A hard freeze (28°F) usually ends earlier, around Jan 11. Springs here are erratic: 69 days separate the 90% and 10% dates, versus a median of 36 days for cities on this site, so watch the forecast rather than the calendar.
When should I plant tomatoes in Napa, CA?
Start seeds indoors Jan 2 – Jan 16 and set transplants outside Mar 6 – Mar 20, once nights stay above 50°F and the soil is near 60°F. With about 274 frost-free days, frost is not the main limit — fruit set drops when nights stay above about 75°F, so early plantings tend to do best. More: tomato planting dates by zone.
How long is the growing season in Napa?
About 299 days without a 32°F frost in a typical (median) year. In 9 years out of 10 the season lasts at least 257 days, and in 1 year in 10 it runs 338 days or more. In fall there is a 10% chance of frost by Nov 15 and a 30% chance by Nov 28. That ranks 70th longest of 84 California cities on this site.
When should I plant a fall garden in Napa?
Count back from the first fall frost (Nov 28): transplant broccoli Sep 5 – Sep 19; sow kale Sep 19 – Oct 17; sow lettuce Sep 19 – Oct 17; sow radishes Oct 17 – Nov 14. Hardy crops keep growing through light frosts; the median 28°F hard freeze here is Dec 19. How the math works: succession and fall planting.
Did Napa's hardiness zone change on the 2023 map?
No. Going by the zone that covers most of the city's land, Napa is zone 9b on both the 2012 and the 2023 USDA maps (PRISM/OSU ZIP listings). About 42% of U.S. ZIP codes kept their half-zone in 2023. Why the 2023 map is warmer.
How does Napa compare with Vallejo, CA?
Both are in zone 9b. The typical last spring frost in Napa (Feb 27) comes about 26 days earlier than in Vallejo, CA (Mar 25), 13 miles away, and the first fall frost is Nov 28 versus Nov 12. The two cities use different NOAA stations.