Last spring frost
Feb 3
Frost Dates for Santa Rosa, CA
First fall frost
Dec 4
Growing season
306 days
Hardiness zone
9b
In an average year around Santa Rosa, CA, the last spring frost (32°F) is about Feb 3 and the first fall frost is about Dec 4, giving roughly a 306-day growing season. To be safe most years, wait until Dec 28 before setting out tender plants.
Last spring frost
Dates the last frost of spring typically ends. Plant tender crops after the risk has passed for your comfort level.
| Frost intensity | Early (10%) | Average (50%) | Late (90%) |
|---|---|---|---|
| Light (36°F) | Apr 17 | Mar 19 | Feb 14 |
| Freeze (32°F) | Mar 13 | Feb 3 | Dec 28 |
| Hard (28°F) | Feb 9 | Jan 5 | Dec 11 |
| Severe (24°F) | Feb 2 | Dec 28 | Dec 3 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 17 | Apr 9 | Apr 1 | Mar 27 | Mar 19 | Mar 13 | Mar 7 | Feb 27 | Feb 14 |
| 32°F | Mar 13 | Feb 28 | Feb 22 | Feb 11 | Feb 3 | Jan 28 | Jan 19 | Jan 7 | Dec 28 |
| 28°F | Feb 9 | Jan 30 | Jan 19 | Jan 11 | Jan 5 | Dec 31 | Dec 25 | Dec 19 | Dec 11 |
| 24°F | Feb 2 | Jan 10 | Jan 4 | Dec 31 | Dec 28 | Dec 22 | Dec 16 | Dec 9 | Dec 3 |
First fall frost
Dates the first frost of fall typically arrives. Count back by a crop's days-to-maturity to know your planting cutoff.
| Frost intensity | Early (10%) | Average (50%) | Late (90%) |
|---|---|---|---|
| Light (36°F) | Oct 31 | Nov 18 | Dec 5 |
| Freeze (32°F) | Nov 14 | Dec 4 | Jan 1 |
| Hard (28°F) | Nov 27 | Dec 17 | Jan 18 |
| Severe (24°F) | Dec 1 | Dec 23 | Jan 25 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Oct 31 | Nov 5 | Nov 9 | Nov 13 | Nov 18 | Nov 21 | Nov 25 | Nov 30 | Dec 5 |
| 32°F | Nov 14 | Nov 21 | Nov 27 | Dec 1 | Dec 4 | Dec 8 | Dec 12 | Dec 18 | Jan 1 |
| 28°F | Nov 27 | Dec 3 | Dec 7 | Dec 12 | Dec 17 | Dec 22 | Dec 30 | Jan 5 | Jan 18 |
| 24°F | Dec 1 | Dec 7 | Dec 12 | Dec 15 | Dec 23 | Dec 28 | Jan 1 | Jan 6 | Jan 25 |
Growing season is measured at 32°F with about 50% probability. Hardiness zone from the 2023 USDA map; frost normals from NOAA 1991-2020.
Where this data comes from
@endif These dates are computed from the nearest official weather station with long-term records: Saint Helena, Ca, about 6.5 miles away@if(!empty($station['elevation_ft'])), at 225 ft elevation. The further the station and the greater the elevation difference from your yard, the more your local frost timing can vary.
How we calculate these dates
Frost and freeze dates come from the NOAA 1991–2020 U.S. Climate Normals, the National Oceanic and Atmospheric Administration's 30-year averages for each weather station. A date shown at the 50% level is the median: in half of years the frost falls on or before it. The 10% and 90% columns show the early and late ends of the range, so you can plant on the odds you're comfortable with. These are long-term averages, not a forecast for this year - always check your local outlook before planting.
Source: NOAA National Centers for Environmental Information, 1991–2020 Climate Normals (public domain). Harman is not affiliated with or endorsed by NOAA.
Frequently asked questions
When is the last frost in Santa Rosa, CA?
On average, the last spring frost (32°F) around Santa Rosa, CA is about Feb 3. In cooler years it can run later, so for a safer bet many gardeners wait until Dec 28.
When is the first frost in the fall?
The first fall frost around Santa Rosa, CA typically arrives about Dec 4. Count back by a crop's days to maturity to find the latest date you can plant it.
When can I plant tomatoes and other tender crops?
Tender crops like tomatoes, peppers and basil are damaged by frost, so wait until the last spring frost has passed - around Feb 3 on average, or Dec 28 to be safe most years.
How long is the growing season here?
The frost-free growing season (between the last spring and first fall 32°F frost) is about 306 days in a typical year.
Are these dates a forecast for this year?
No. They are 30-year averages from the NOAA 1991–2020 Climate Normals, not a prediction for the current year. Use them for planning and always check your local weather forecast before planting or protecting crops.
Local weather for 95409 Planting calendar → California frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026