Frost dates for Fort Ross, CA
At Fort Ross, the median last spring frost (32°F) is Feb 26 and the median first fall frost is Dec 27, for a typical growing season of 310 days. For a 90% chance that the last frost has passed, wait until May 1. Nearby ZIP codes are in USDA hardiness zones 9b to 10a.
- Feb 26Last spring frost (median)50% chance of 32°F after this date
- May 1Safer planting date10% chance of 32°F after this date
- Dec 27First fall frost (median)50% chance of 32°F by this date
- 310 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 11 | Apr 17 | May 19 |
| 32°F | Dec 27 | Feb 26 | May 1 |
| 28°F | Dec 9 | Jan 29 | Apr 28 |
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 20 | Nov 25 | Dec 24 |
| 32°F | Dec 1 | Dec 27 | Feb 27 |
| 28°F | Dec 5 | Jan 16 | Apr 18 |
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 | 179 days | 222 days | 266 days |
| 32°F | 240 days | 310 days | 365 days |
| 28°F | 314 days | 365 days | 365 days |
| 24°F | 365 days | 365 days | 365 days |
Chance of a freeze in any year
| Temperature | Chance per year |
|---|---|
| 36°F | 100% |
| 32°F | 87% |
| 28°F | 28% |
| 24°F | 0% |
ZIP codes whose closest station is this one
| ZIP | Hardiness zone | Avg. extreme low | Distance |
|---|---|---|---|
| 95450 | 10a | 30 to 35°F | 3 km |
| 95421 | 9b | 25 to 30°F | 9 km |
| 95480 | 10a | 30 to 35°F | 22 km |
| 95412 | 9b | 25 to 30°F | 23 km |
| 95497 | 10a | 30 to 35°F | 30 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 USC00043191, at 38.5150, -123.2447, elevation 34 m (112 ft).
- Data quality: Representative (10+ years), 17 years of freeze data.
- Average days per year at or below 32°F: 12.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Bodega 6 WSW (26 km)
- Occidental (28 km)
- Graton (34 km)
- Healdsburg (35 km)
- Cloverdale (36 km)
- Santa Rosa Sonoma Co Airport (38 km)
- Santa Rosa (47 km)
- Calistoga (57 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.