Vacaville, California: planting zone & frost dates
Vacaville 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 Mar 3 and the first fall frost around Nov 21.
Frost dates
| Probability | Last spring frost (32°F) | First fall frost (32°F) |
|---|---|---|
| Safer (10% risk) | Mar 25 | Nov 12 |
| Typical planning date (30% risk) | Mar 3 | Nov 21 |
| Median (50%) | Feb 18 | Nov 28 |
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 VACAVILLE NUT TREE AP, CA (USW00093241), 1.4 mi (2.3 km) from the city center and 59 ft lower than the city center (-18 m). Record used for the 1991–2020 normals: 17 years.
Why your yard may differ from the station: microclimates.
Hardiness zone across Vacaville
All 3 ZIP codes covering Vacaville are in zone 9b.
Vegetable planting calendar for Vacaville
Dates are counted from the 30%-risk frost dates above (last frost Mar 3, first frost Nov 21). 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 6 – Jan 20 | Mar 10 – Mar 24 | — | — |
| Pepper | Dec 23 – Jan 6 | Mar 17 – Mar 31 | — | — |
| Lettuce | Jan 20 – Feb 3 | Feb 17 – Mar 10 | Feb 3 – Mar 17 | Sep 12 – Oct 10 |
| Green Beans | — | — | Mar 10 – Apr 14 | Aug 29 – Sep 12 |
| Sweet Corn | — | — | Mar 10 – Apr 7 | — |
| Zucchini & Summer Squash | Feb 3 – Feb 10 | Mar 10 – Mar 24 | Mar 10 – Mar 31 | Aug 29 – Sep 12 |
| Cucumber | Feb 3 – Feb 10 | Mar 17 – Mar 24 | Mar 10 – Mar 31 | Aug 29 – Sep 12 |
| Carrot | — | — | Feb 10 – Mar 17 | Aug 29 – Sep 12 |
| Onion | Dec 9 – Dec 23 | Feb 3 – Feb 17 | — | — |
| Potato | — | Feb 3 – Feb 24 | — | — |
| Basil | Jan 20 – Feb 3 | Mar 17 – Mar 31 | Mar 17 – Apr 7 | — |
| Spinach | — | — | Jan 20 – Feb 17 | Sep 26 – Oct 24 |
| Kale | Jan 6 – Jan 20 | Feb 3 – Feb 24 | Feb 3 – Feb 24 | Sep 12 – Oct 10 |
| Broccoli | Jan 6 – Jan 20 | Feb 17 – Mar 10 | — | Aug 29 – Sep 12 |
| Peas | — | — | Jan 20 – Feb 10 | Sep 12 – Sep 26 |
| Eggplant | Dec 23 – Jan 6 | Mar 17 – Mar 31 | — | — |
| Cabbage | Jan 6 – Jan 20 | Feb 3 – Feb 17 | — | Aug 29 – Sep 12 |
| Radish | — | — | Jan 27 – Mar 17 | Oct 10 – Nov 7 |
| Strawberry | — | Feb 3 – Feb 24 | — | — |
| Beets | — | — | Feb 10 – Mar 24 | Sep 12 – Sep 26 |
Nearby cities in California
- Fairfield — zone 9b, last frost Jan 28, first frost Dec 7
- Napa — zone 9b, last frost Feb 27, first frost Nov 28
- Pittsburg — zone 9b, last frost Jan 22, first frost Dec 10
- Vallejo — zone 9b, last frost Mar 25, first frost Nov 12
- Concord — zone 9b, last frost Jan 23, first frost Dec 6
- Antioch — zone 9b, last frost Jan 22, first frost Dec 10
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
Vacaville gardening questions
When is the last frost in Vacaville, CA?
Plan around Mar 3. At NOAA's Vacaville Nut Tree Airport, CA station, 1.4 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 18, and after Mar 25 the risk drops to about 1 in 10. A hard freeze (28°F) usually ends earlier, around Jan 15. Springs here are erratic: 73 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 Vacaville, CA?
Start seeds indoors Jan 6 – Jan 20 and set transplants outside Mar 10 – Mar 24, once nights stay above 50°F and the soil is near 60°F. With about 263 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 Vacaville?
About 283 days without a 32°F frost in a typical (median) year. In 9 years out of 10 the season lasts at least 245 days, and in 1 year in 10 it runs 325 days or more. In fall there is a 10% chance of frost by Nov 12 and a 30% chance by Nov 21. That ranks 73rd longest of 84 California cities on this site.
When should I plant a fall garden in Vacaville?
Count back from the first fall frost (Nov 21): transplant broccoli Aug 29 – Sep 12; sow kale Sep 12 – Oct 10; sow lettuce Sep 12 – Oct 10; sow radishes Oct 10 – Nov 7. Hardy crops keep growing through light frosts; the median 28°F hard freeze here is Dec 10. How the math works: succession and fall planting.
Did Vacaville's hardiness zone change on the 2023 map?
No. Going by the zone that covers most of the city's land, Vacaville 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 Vacaville compare with Fairfield, CA?
Both are in zone 9b. The typical last spring frost in Vacaville (Mar 3) comes about 34 days later than in Fairfield, CA (Jan 28), 8 miles away, and the first fall frost is Nov 21 versus Dec 7. The two cities use different NOAA stations.