Last spring frost
Feb 14
Frost Dates for Princeton, CA
First fall frost
Dec 1
Growing season
293 days
Hardiness zone
9b
In an average year around Princeton, CA, the last spring frost (32°F) is about Feb 14 and the first fall frost is about Dec 1, giving roughly a 293-day growing season. To be safe most years, wait until Jan 2 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 22 | Mar 31 | Feb 21 |
| Freeze (32°F) | Mar 31 | Feb 14 | Jan 2 |
| Hard (28°F) | Feb 20 | Jan 8 | Dec 11 |
| Severe (24°F) | Jan 27 | Dec 31 | Dec 5 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 22 | Apr 15 | Apr 9 | Apr 5 | Mar 31 | Mar 24 | Mar 14 | Mar 4 | Feb 21 |
| 32°F | Mar 31 | Mar 13 | Feb 28 | Feb 22 | Feb 14 | Feb 5 | Jan 27 | Jan 16 | Jan 2 |
| 28°F | Feb 20 | Feb 5 | Jan 22 | Jan 14 | Jan 8 | Jan 2 | Dec 29 | Dec 21 | Dec 11 |
| 24°F | Jan 27 | Jan 14 | Jan 6 | Jan 2 | Dec 31 | Dec 24 | Dec 17 | Dec 12 | Dec 5 |
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 28 | Nov 12 | Nov 30 |
| Freeze (32°F) | Nov 11 | Dec 1 | Dec 26 |
| Hard (28°F) | Nov 24 | Dec 15 | Jan 17 |
| Severe (24°F) | Dec 2 | Dec 22 | Jan 22 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Oct 28 | Nov 2 | Nov 5 | Nov 9 | Nov 12 | Nov 16 | Nov 20 | Nov 24 | Nov 30 |
| 32°F | Nov 11 | Nov 17 | Nov 23 | Nov 27 | Dec 1 | Dec 4 | Dec 8 | Dec 13 | Dec 26 |
| 28°F | Nov 24 | Dec 1 | Dec 6 | Dec 10 | Dec 15 | Dec 19 | Dec 28 | Jan 2 | Jan 17 |
| 24°F | Dec 2 | Dec 8 | Dec 12 | Dec 16 | Dec 22 | Dec 29 | Jan 2 | Jan 6 | Jan 22 |
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: Colusa 2 Ssw, Ca, about 15.5 miles away@if(!empty($station['elevation_ft'])), at 50 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 Princeton, CA?
On average, the last spring frost (32°F) around Princeton, CA is about Feb 14. In cooler years it can run later, so for a safer bet many gardeners wait until Jan 2.
When is the first frost in the fall?
The first fall frost around Princeton, CA typically arrives about Dec 1. 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 14 on average, or Jan 2 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 293 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 95970 Planting calendar → California frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026