Last spring frost
Jan 19
Frost Dates for Byron, CA
First fall frost
Dec 10
Growing season
330 days
Hardiness zone
9b
In an average year around Byron, CA, the last spring frost (32°F) is about Jan 19 and the first fall frost is about Dec 10, giving roughly a 330-day growing season. To be safe most years, wait until Dec 25 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) | Mar 24 | Feb 21 | Jan 22 |
| Freeze (32°F) | Feb 17 | Jan 19 | Dec 25 |
| Hard (28°F) | Jan 22 | Jan 1 | Dec 12 |
| Severe (24°F) | Jan 11 | Dec 31 | Dec 13 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Mar 24 | Mar 9 | Mar 1 | Feb 25 | Feb 21 | Feb 13 | Feb 7 | Jan 31 | Jan 22 |
| 32°F | Feb 17 | Feb 6 | Jan 31 | Jan 25 | Jan 19 | Jan 13 | Jan 8 | Jan 2 | Dec 25 |
| 28°F | Jan 22 | Jan 15 | Jan 9 | Jan 5 | Jan 1 | Dec 30 | Dec 26 | Dec 21 | Dec 12 |
| 24°F | Jan 11 | Jan 7 | Jan 4 | Jan 2 | Dec 31 | Dec 28 | Dec 21 | Dec 17 | Dec 13 |
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 13 | Nov 29 | Dec 13 |
| Freeze (32°F) | Nov 26 | Dec 10 | Jan 7 |
| Hard (28°F) | Dec 4 | Dec 22 | Jan 10 |
| Severe (24°F) | Dec 10 | Dec 30 | Jan 9 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Nov 13 | Nov 19 | Nov 23 | Nov 26 | Nov 29 | Dec 1 | Dec 4 | Dec 8 | Dec 13 |
| 32°F | Nov 26 | Dec 1 | Dec 4 | Dec 7 | Dec 10 | Dec 15 | Dec 20 | Dec 27 | Jan 7 |
| 28°F | Dec 4 | Dec 10 | Dec 14 | Dec 18 | Dec 22 | Dec 26 | Dec 31 | Jan 4 | Jan 10 |
| 24°F | Dec 10 | Dec 17 | Dec 20 | Dec 24 | Dec 30 | Jan 1 | Jan 3 | Jan 6 | Jan 9 |
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: Tracy Pumping Plt, Ca, about 3.5 miles away@if(!empty($station['elevation_ft'])), at 61 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 Byron, CA?
On average, the last spring frost (32°F) around Byron, CA is about Jan 19. In cooler years it can run later, so for a safer bet many gardeners wait until Dec 25.
When is the first frost in the fall?
The first fall frost around Byron, CA typically arrives about Dec 10. 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 Jan 19 on average, or Dec 25 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 330 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 94514 Planting calendar → California frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026