Last spring frost
Feb 15
Frost Dates for Guerneville, CA
First fall frost
Dec 2
Growing season
292 days
Hardiness zone
9b
In an average year around Guerneville, CA, the last spring frost (32°F) is about Feb 15 and the first fall frost is about Dec 2, giving roughly a 292-day growing season. To be safe most years, wait until Jan 4 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 20 | Mar 29 | Feb 27 |
| Freeze (32°F) | Mar 17 | Feb 15 | Jan 4 |
| Hard (28°F) | Feb 2 | Jan 7 | Dec 14 |
| Severe (24°F) | Jan 28 | Jan 1 | Dec 10 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 20 | Apr 13 | Apr 7 | Apr 2 | Mar 29 | Mar 23 | Mar 15 | Mar 8 | Feb 27 |
| 32°F | Mar 17 | Mar 6 | Feb 28 | Feb 23 | Feb 15 | Feb 8 | Jan 31 | Jan 21 | Jan 4 |
| 28°F | Feb 2 | Jan 28 | Jan 21 | Jan 14 | Jan 7 | Jan 2 | Dec 29 | Dec 23 | Dec 14 |
| 24°F | Jan 28 | Jan 19 | Jan 13 | Jan 6 | Jan 1 | Dec 31 | Dec 24 | Dec 18 | Dec 10 |
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) | Nov 1 | Nov 16 | Dec 2 |
| Freeze (32°F) | Nov 14 | Dec 2 | Jan 1 |
| Hard (28°F) | Nov 28 | Dec 17 | Jan 12 |
| Severe (24°F) | Dec 4 | Dec 30 | Jan 25 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Nov 1 | Nov 5 | Nov 9 | Nov 12 | Nov 16 | Nov 21 | Nov 24 | Nov 27 | Dec 2 |
| 32°F | Nov 14 | Nov 21 | Nov 26 | Nov 29 | Dec 2 | Dec 6 | Dec 10 | Dec 17 | Jan 1 |
| 28°F | Nov 28 | Dec 2 | Dec 7 | Dec 12 | Dec 17 | Dec 22 | Dec 30 | Jan 3 | Jan 12 |
| 24°F | Dec 4 | Dec 10 | Dec 15 | Dec 23 | Dec 30 | Jan 1 | Jan 7 | Jan 15 | 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: Healdsburg, Ca, about 8.9 miles away@if(!empty($station['elevation_ft'])), at 177 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 Guerneville, CA?
On average, the last spring frost (32°F) around Guerneville, CA is about Feb 15. In cooler years it can run later, so for a safer bet many gardeners wait until Jan 4.
When is the first frost in the fall?
The first fall frost around Guerneville, CA typically arrives about Dec 2. 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 15 on average, or Jan 4 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 292 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 95471 Planting calendar → California frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026