Frost dates in Santa Rosa, California
NOAA 1991–2020 normals for a 32 °F freeze. Low spots and the edge of town run colder than downtown.
Short answer
The average last spring frost in Santa Rosa is March 2, and the average first fall frost is November 20, from NOAA's Santa Rosa Sonoma Co Airport station, 7 miles from the middle of Santa Rosa. 1 year in 10 the last frost comes after April 2, and the first one by November 1. That leaves about 263 frost-free days. Santa Rosa is in USDA planting zone 9a.
Weather stations around Santa Rosa
The first row is the date most people in Santa Rosa go by. The others show how far the dates move across the area.
| Station | Last spring frost | First fall frost | Frost-free |
|---|---|---|---|
| Santa Rosa Sonoma Co Airport 7 mi away, 114 ft | March 2 1 in 10 after April 2 | November 20 1 in 10 by November 1 | 263 days |
| Santa Rosa 1 mi away, 166 ft | February 25 1 in 10 after March 29 | December 1 1 in 10 by November 10 | 279 days |
| Graton 9 mi away, 200 ft | March 20 1 in 10 after April 19 | November 13 1 in 10 by October 26 | 238 days |
| Calistoga 12 mi away, 400 ft | March 2 1 in 10 after April 18 | November 23 1 in 10 by November 1 | 266 days |
| Saint Helena 13 mi away, 225 ft | February 3 1 in 10 after March 13 | December 4 1 in 10 by November 14 | 304 days |
Distances are from the middle of Santa Rosa as the Census Bureau maps it. The average date is NOAA's 50% date: half of years have a later last frost, or an earlier first one. Plan by the 1-in-10 date if a freeze would cost you plants. The planting zone is the USDA 2023 zone for ZIP code 95405, at the middle of the city.
Your exact ZIP code
Santa Rosa covers a lot of ground. For the station nearest your own street, and its planting zone, type your ZIP code.
How these dates work
Frost dates come from NOAA's 1991 to 2020 Climate Normals, which work out from each weather station's daily lows how likely the last spring freeze and the first fall freeze (32 °F) are by each date. We use the station nearest the middle of your ZIP code and show its height and distance, since a station on a hill or by a lake can differ from your yard.
The average date is the 50% date: half of years have a freeze after the spring date or before the fall one. The 1-in-10 dates are NOAA's 10% dates, the ones to plan by if a late freeze would cost you plants. Within one yard, cold air pools in low spots while walls and paving hold heat, so some corners freeze before others.
More frost dates
All of California, station by station.
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Where the numbers come from
- USDA Plant Hardiness Zone Map, 2023. Agricultural Research Service, U.S. Department of Agriculture
- PRISM Climate Group, Oregon State University (zone data)
- NOAA NCEI, U.S. Climate Normals 1991–2020, annual/seasonal
- NOAA, Normals calculation methodology (frost-freeze probability dates)
- US Census Bureau, 2025 ZCTA gazetteer (ZIP code centers)
- US Census Bureau, 2025 city population estimates and place gazetteer