Frost dates for Santa Rosa Sonoma Co Airport, CA
At Santa Rosa Sonoma Co Airport, the median last spring frost (32°F) is Mar 2 and the median first fall frost is Nov 20, for a typical growing season of 262 days. For a 90% chance that the last frost has passed, wait until Apr 2. Nearby ZIP codes are in USDA hardiness zone 9a.
- Mar 2Last spring frost (median)50% chance of 32°F after this date
- Apr 2Safer planting date10% chance of 32°F after this date
- Nov 20First fall frost (median)50% chance of 32°F by this date
- 262 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 17 | Apr 12 | May 1 |
| 32°F | Jan 27 | Mar 2 | Apr 2 |
| 28°F | Dec 20 | Jan 23 | Feb 23 |
| 24°F | Dec 6 | Dec 31 | Jan 27 |
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 16 | Nov 3 | Nov 21 |
| 32°F | Nov 1 | Nov 20 | Dec 10 |
| 28°F | Nov 15 | Dec 5 | Jan 7 |
| 24°F | Nov 29 | Dec 19 | Jan 17 |
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 | 177 days | 206 days | 237 days |
| 32°F | 223 days | 262 days | 307 days |
| 28°F | 284 days | 321 days | 361 days |
| 24°F | 329 days | 365 days | 365 days |
Chance of a freeze in any year
| Temperature | Chance per year |
|---|---|
| 36°F | 100% |
| 32°F | 100% |
| 28°F | 90% |
| 24°F | 45% |
ZIP codes whose closest station is this one
| ZIP | Hardiness zone | Avg. extreme low | Distance |
|---|---|---|---|
| 95492 | 9a | 20 to 25°F | 3 km |
| 95439 | 9a | 20 to 25°F | 3 km |
| 95403 | 9a | 20 to 25°F | 5 km |
| 95401 | 9a | 20 to 25°F | 6 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 USW00023213, at 38.5039, -122.8103, elevation 35 m (114 ft).
- Data quality: Representative (10+ years), 21 years of freeze data.
- Average days per year at or below 32°F: 31.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Graton (9 km)
- Santa Rosa (10 km)
- Healdsburg (15 km)
- Occidental (19 km)
- Calistoga (21 km)
- Saint Helena (29 km)
- Bodega 6 WSW (31 km)
- Petaluma Airport (33 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.