Last spring frost
Mar 5
Frost Dates for American Canyon, CA
First fall frost
Nov 21
Growing season
256 days
Hardiness zone
9b
In an average year around American Canyon, CA, the last spring frost (32°F) is about Mar 5 and the first fall frost is about Nov 21, giving roughly a 256-day growing season. To be safe most years, wait until Jan 26 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) | May 9 | Apr 17 | Mar 17 |
| Freeze (32°F) | Apr 16 | Mar 5 | Jan 26 |
| Hard (28°F) | Feb 28 | Jan 23 | Dec 20 |
| Severe (24°F) | Feb 2 | Dec 31 | Dec 6 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | May 9 | Apr 30 | Apr 27 | Apr 22 | Apr 17 | Apr 12 | Apr 6 | Mar 30 | Mar 17 |
| 32°F | Apr 16 | Apr 4 | Mar 25 | Mar 14 | Mar 5 | Feb 28 | Feb 20 | Feb 8 | Jan 26 |
| 28°F | Feb 28 | Feb 17 | Feb 6 | Jan 31 | Jan 23 | Jan 14 | Jan 6 | Dec 29 | Dec 20 |
| 24°F | Feb 2 | Jan 21 | Jan 14 | Jan 6 | Dec 31 | Dec 27 | Dec 21 | Dec 13 | Dec 6 |
| 20°F | Jan 20 | Jan 10 | Jan 3 | Dec 31 | Dec 28 | Dec 20 | Dec 15 | Dec 11 | Dec 4 |
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 16 | Nov 4 | Nov 22 |
| Freeze (32°F) | Nov 3 | Nov 21 | Dec 13 |
| Hard (28°F) | Nov 16 | Dec 5 | Jan 11 |
| Severe (24°F) | Nov 28 | Dec 17 | Jan 23 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Oct 16 | Oct 24 | Oct 29 | Nov 1 | Nov 4 | Nov 6 | Nov 10 | Nov 15 | Nov 22 |
| 32°F | Nov 3 | Nov 8 | Nov 12 | Nov 17 | Nov 21 | Nov 25 | Nov 29 | Dec 3 | Dec 13 |
| 28°F | Nov 16 | Nov 22 | Nov 28 | Dec 1 | Dec 5 | Dec 12 | Dec 18 | Dec 30 | Jan 11 |
| 24°F | Nov 28 | Dec 2 | Dec 7 | Dec 12 | Dec 17 | Dec 24 | Jan 1 | Jan 9 | Jan 23 |
| 20°F | Dec 2 | Dec 6 | Dec 10 | Dec 15 | Dec 21 | Dec 28 | Jan 1 | Jan 6 | Jan 20 |
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: Napa Co Ap, Ca, about 3.7 miles away@if(!empty($station['elevation_ft'])), at 14 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 American Canyon, CA?
On average, the last spring frost (32°F) around American Canyon, CA is about Mar 5. In cooler years it can run later, so for a safer bet many gardeners wait until Jan 26.
When is the first frost in the fall?
The first fall frost around American Canyon, CA typically arrives about Nov 21. 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 Mar 5 on average, or Jan 26 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 256 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 94503 Planting calendar → California frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026