Frost dates for Vacaville, CA
At Vacaville, the median last spring frost (32°F) is Jan 31 and the median first fall frost is Dec 11, for a typical growing season of 318 days. For a 90% chance that the last frost has passed, wait until Mar 11. Nearby ZIP codes are in USDA hardiness zone 9b.
- Jan 31Last spring frost (median)50% chance of 32°F after this date
- Mar 11Safer planting date10% chance of 32°F after this date
- Dec 11First fall frost (median)50% chance of 32°F by this date
- 318 daysGrowing season (median)between 32°F freezes
Last spring frost dates
The chance that the temperature drops to the threshold after each date.
| Temperature | 90% chance later | 50% chance later | 10% chance later |
|---|---|---|---|
| 36°F | Feb 4 | Mar 8 | Apr 7 |
| 32°F | Dec 30 | Jan 31 | Mar 11 |
| 28°F | Dec 16 | Jan 6 | Jan 31 |
| 24°F | Dec 11 | Dec 30 | Jan 16 |
First fall frost dates
The chance that the temperature has dropped to the threshold by each date.
| Temperature | 10% chance by | 50% chance by | 90% chance by |
|---|---|---|---|
| 36°F | Nov 10 | Nov 26 | Dec 13 |
| 32°F | Nov 24 | Dec 11 | Jan 12 |
| 28°F | Dec 4 | Dec 23 | Jan 19 |
| 24°F | Dec 9 | Dec 28 | Jan 15 |
Growing season length
Days between the last spring and first fall freeze, as the length reached in 9, 5 and 1 out of 10 years.
| Temperature | 9 in 10 years at least | 5 in 10 years at least | 1 in 10 years at least |
|---|---|---|---|
| 36°F | 226 days | 259 days | 298 days |
| 32°F | 275 days | 318 days | 355 days |
| 28°F | 334 days | 361 days | 365 days |
| 24°F | 363 days | 365 days | 365 days |
Chance of a freeze in any year
| Temperature | Chance per year |
|---|---|
| 36°F | 100% |
| 32°F | 95% |
| 28°F | 54% |
| 24°F | 15% |
ZIP codes whose closest station is this one
| ZIP | Hardiness zone | Avg. extreme low | Distance |
|---|---|---|---|
| 95688 | 9b | 25 to 30°F | 7 km |
Not the official USDA Plant Hardiness Zone Map. Zones shown here are the values published in the USDA-ARS / Oregon State University PRISM Group 2023 ZIP code tables, shown unaltered. For the official interactive map, visit planthardiness.ars.usda.gov.
About this station
- NOAA station ID USC00049200, at 38.3956, -121.9608, elevation 34 m (110 ft).
- Data quality: Representative (10+ years), 18 years of freeze data.
- Average days per year at or below 32°F: 14.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Vacaville Nut Tree Airport (2 km)
- Lake Solano (11 km)
- Winters (14 km)
- Fairfield (16 km)
- Markley Cove (18 km)
- Davis 2 WSW Exp. Farm (22 km)
- Napa State Hospital (30 km)
- Napa Co Airport (35 km)
Sources
- NOAA National Centers for Environmental Information, U.S. Climate Normals 1991–2020, annual/seasonal normals by station (version 1.0.1), file dated June 27, 2023; documentation.
- USDA Agricultural Research Service and PRISM Group, Oregon State University, 2023 Plant Hardiness Zone Map ZIP code tables (CONUS, Alaska, Hawaii, Puerto Rico), files dated November 17, 2023. Data © PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed November 1, 2026. Official map: planthardiness.ars.usda.gov.
- U.S. Census Bureau, 2024 Gazetteer ZIP Code Tabulation Areas file, dated August 30, 2024 (ZIP centroids used to find the nearest station).
Freeze dates are 30-year probabilities, not forecasts. Check your local forecast before planting tender plants.