Last spring frost
Apr 5
Frost Dates for Onyx, CA
First fall frost
Nov 3
Growing season
212 days
Hardiness zone
9a
In an average year around Onyx, CA, the last spring frost (32°F) is about Apr 5 and the first fall frost is about Nov 3, giving roughly a 212-day growing season. To be safe most years, wait until Mar 8 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 1 | Apr 20 | Apr 5 |
| Freeze (32°F) | Apr 21 | Apr 5 | Mar 8 |
| Hard (28°F) | Apr 7 | Mar 6 | Feb 8 |
| Severe (24°F) | Mar 3 | Feb 4 | Jan 2 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | May 1 | Apr 29 | Apr 26 | Apr 23 | Apr 20 | Apr 17 | Apr 14 | Apr 11 | Apr 5 |
| 32°F | Apr 21 | Apr 16 | Apr 12 | Apr 9 | Apr 5 | Mar 30 | Mar 22 | Mar 16 | Mar 8 |
| 28°F | Apr 7 | Mar 30 | Mar 18 | Mar 11 | Mar 6 | Mar 1 | Feb 24 | Feb 18 | Feb 8 |
| 24°F | Mar 3 | Feb 23 | Feb 16 | Feb 9 | Feb 4 | Jan 29 | Jan 20 | Jan 12 | Jan 2 |
| 20°F | Feb 6 | Jan 27 | Jan 17 | Jan 11 | Jan 6 | Jan 1 | Dec 29 | Dec 22 | Dec 11 |
| 16°F | Jan 12 | Jan 7 | Jan 3 | Jan 1 | Dec 28 | Dec 26 | Dec 21 | Dec 18 | Dec 14 |
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 9 | Oct 21 | Nov 5 |
| Freeze (32°F) | Oct 18 | Nov 3 | Nov 16 |
| Hard (28°F) | Oct 31 | Nov 17 | Dec 1 |
| Severe (24°F) | Nov 15 | Dec 1 | Dec 24 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Oct 9 | Oct 13 | Oct 15 | Oct 18 | Oct 21 | Oct 25 | Oct 28 | Nov 1 | Nov 5 |
| 32°F | Oct 18 | Oct 22 | Oct 28 | Oct 31 | Nov 3 | Nov 6 | Nov 9 | Nov 12 | Nov 16 |
| 28°F | Oct 31 | Nov 5 | Nov 9 | Nov 13 | Nov 17 | Nov 20 | Nov 23 | Nov 27 | Dec 1 |
| 24°F | Nov 15 | Nov 21 | Nov 25 | Nov 28 | Dec 1 | Dec 5 | Dec 9 | Dec 15 | Dec 24 |
| 20°F | Nov 27 | Dec 2 | Dec 8 | Dec 12 | Dec 19 | Dec 24 | Dec 31 | Jan 5 | Jan 18 |
| 16°F | Dec 10 | Dec 14 | Dec 19 | Dec 22 | Dec 27 | Dec 30 | Jan 2 | Jan 6 | Jan 11 |
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: S Lake Fs, Ca, about 14.7 miles away@if(!empty($station['elevation_ft'])), at 2,654 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 Onyx, CA?
On average, the last spring frost (32°F) around Onyx, CA is about Apr 5. In cooler years it can run later, so for a safer bet many gardeners wait until Mar 8.
When is the first frost in the fall?
The first fall frost around Onyx, CA typically arrives about Nov 3. 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 Apr 5 on average, or Mar 8 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 212 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 93255 Planting calendar → California frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026