Frost dates for Sonoma, CA
At Sonoma, the median last spring frost (32°F) is Mar 2 and the median first fall frost is Nov 27, for a typical growing season of 270 days. For a 90% chance that the last frost has passed, wait until Apr 5. Nearby ZIP codes are in USDA hardiness zone 9b.
- Mar 2Last spring frost (median)50% chance of 32°F after this date
- Apr 5Safer planting date10% chance of 32°F after this date
- Nov 27First fall frost (median)50% chance of 32°F by this date
- 270 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 | Mar 14 | Apr 8 | Apr 29 |
| 32°F | Jan 27 | Mar 2 | Apr 5 |
| 28°F | Dec 20 | Jan 20 | Feb 22 |
| 24°F | Dec 10 | Jan 1 | Jan 29 |
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 | Oct 25 | Nov 8 | Nov 26 |
| 32°F | Nov 6 | Nov 27 | Dec 21 |
| 28°F | Nov 24 | Dec 14 | Jan 17 |
| 24°F | Dec 3 | Dec 28 | Jan 23 |
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 | 187 days | 214 days | 247 days |
| 32°F | 230 days | 270 days | 310 days |
| 28°F | 292 days | 334 days | 365 days |
| 24°F | 338 days | 365 days | 365 days |
Chance of a freeze in any year
| Temperature | Chance per year |
|---|---|
| 36°F | 100% |
| 32°F | 100% |
| 28°F | 87% |
| 24°F | 36% |
ZIP codes whose closest station is this one
| ZIP | Hardiness zone | Avg. extreme low | Distance |
|---|---|---|---|
| 95476 | 9b | 25 to 30°F | 5 km |
| 95431 | 9b | 25 to 30°F | 7 km |
| 95442 | 9b | 25 to 30°F | 10 km |
| 94599 | 9b | 25 to 30°F | 13 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 USC00048351, at 38.2994, -122.4622, elevation 30 m (97 ft).
- Data quality: Standard (24+ years of data), 30 years of freeze data.
- Average days per year at or below 32°F: 21.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Petaluma Airport (14 km)
- Napa State Hospital (17 km)
- Napa Co Airport (18 km)
- Saint Helena (23 km)
- Santa Rosa (28 km)
- Angwin Pacific Union College (30 km)
- Vallejo (33 km)
- San Rafael Civic Center (34 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.