Last spring frost
Feb 12
Frost Dates for Napa, CA
First fall frost
Dec 4
Growing season
299 days
Hardiness zone
9b
In an average year around Napa, CA, the last spring frost (32°F) is about Feb 12 and the first fall frost is about Dec 4, giving roughly a 299-day growing season. To be safe most years, wait until Jan 3 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 19 | Mar 27 | Feb 26 |
| Freeze (32°F) | Mar 13 | Feb 12 | Jan 3 |
| Hard (28°F) | Feb 13 | Jan 11 | Dec 16 |
| Severe (24°F) | Jan 22 | Dec 30 | Dec 7 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 19 | Apr 11 | Apr 5 | Mar 31 | Mar 27 | Mar 21 | Mar 14 | Mar 6 | Feb 26 |
| 32°F | Mar 13 | Mar 3 | Feb 27 | Feb 20 | Feb 12 | Feb 5 | Jan 29 | Jan 18 | Jan 3 |
| 28°F | Feb 13 | Feb 1 | Jan 26 | Jan 17 | Jan 11 | Jan 3 | Dec 29 | Dec 24 | Dec 16 |
| 24°F | Jan 22 | Jan 11 | Jan 5 | Jan 1 | Dec 30 | Dec 26 | Dec 20 | Dec 14 | Dec 7 |
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 17 | Dec 4 |
| Freeze (32°F) | Nov 15 | Dec 4 | Jan 4 |
| Hard (28°F) | Dec 1 | Dec 19 | Jan 23 |
| Severe (24°F) | Dec 5 | Dec 25 | Jan 19 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Oct 31 | Nov 4 | Nov 10 | Nov 13 | Nov 17 | Nov 22 | Nov 26 | Nov 30 | Dec 4 |
| 32°F | Nov 15 | Nov 23 | Nov 28 | Dec 1 | Dec 4 | Dec 7 | Dec 13 | Dec 20 | Jan 4 |
| 28°F | Dec 1 | Dec 5 | Dec 9 | Dec 14 | Dec 19 | Dec 26 | Jan 1 | Jan 8 | Jan 23 |
| 24°F | Dec 5 | Dec 9 | Dec 15 | Dec 21 | Dec 25 | Dec 31 | Jan 3 | Jan 8 | Jan 19 |
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 State Hospital, Ca, about 2.5 miles away@if(!empty($station['elevation_ft'])), at 35 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 Napa, CA?
On average, the last spring frost (32°F) around Napa, CA is about Feb 12. In cooler years it can run later, so for a safer bet many gardeners wait until Jan 3.
When is the first frost in the fall?
The first fall frost around Napa, 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 12 on average, or Jan 3 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 299 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 94559 Planting calendar → California frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026