Last spring frost
Jun 6
Frost Dates for Mount Hebron, CA
First fall frost
Sep 28
Growing season
113 days
Hardiness zone
6b
In an average year around Mount Hebron, CA, the last spring frost (32°F) is about Jun 6 and the first fall frost is about Sep 28, giving roughly a 113-day growing season. To be safe most years, wait until May 16 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) | Jul 3 | Jun 19 | Jun 4 |
| Freeze (32°F) | Jun 22 | Jun 6 | May 16 |
| Hard (28°F) | Jun 9 | May 16 | Apr 24 |
| Severe (24°F) | May 22 | Apr 24 | Apr 5 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Jul 3 | Jun 29 | Jun 25 | Jun 22 | Jun 19 | Jun 15 | Jun 13 | Jun 9 | Jun 4 |
| 32°F | Jun 22 | Jun 16 | Jun 13 | Jun 9 | Jun 6 | Jun 3 | May 30 | May 24 | May 16 |
| 28°F | Jun 9 | Jun 3 | May 28 | May 22 | May 16 | May 11 | May 4 | Apr 29 | Apr 24 |
| 24°F | May 22 | May 11 | May 3 | Apr 28 | Apr 24 | Apr 21 | Apr 17 | Apr 12 | Apr 5 |
| 20°F | Apr 26 | Apr 18 | Apr 13 | Apr 8 | Apr 4 | Mar 31 | Mar 24 | Mar 18 | Mar 8 |
| 16°F | Apr 6 | Mar 28 | Mar 21 | Mar 13 | Mar 6 | Mar 1 | Feb 24 | Feb 17 | Feb 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) | Aug 25 | Sep 13 | Sep 29 |
| Freeze (32°F) | Sep 8 | Sep 28 | Oct 17 |
| Hard (28°F) | Sep 26 | Oct 15 | Nov 1 |
| Severe (24°F) | Oct 12 | Oct 30 | Nov 14 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Aug 25 | Sep 1 | Sep 6 | Sep 9 | Sep 13 | Sep 16 | Sep 19 | Sep 24 | Sep 29 |
| 32°F | Sep 8 | Sep 15 | Sep 20 | Sep 25 | Sep 28 | Oct 2 | Oct 6 | Oct 11 | Oct 17 |
| 28°F | Sep 26 | Oct 1 | Oct 6 | Oct 11 | Oct 15 | Oct 18 | Oct 22 | Oct 27 | Nov 1 |
| 24°F | Oct 12 | Oct 18 | Oct 22 | Oct 27 | Oct 30 | Nov 2 | Nov 5 | Nov 9 | Nov 14 |
| 20°F | Oct 22 | Oct 30 | Nov 3 | Nov 7 | Nov 11 | Nov 14 | Nov 18 | Nov 22 | Nov 28 |
| 16°F | Nov 2 | Nov 10 | Nov 16 | Nov 20 | Nov 24 | Nov 28 | Dec 1 | Dec 5 | Dec 13 |
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: Lava Beds Nat Mon, Ca, about 21 miles away@if(!empty($station['elevation_ft'])), at 4,770 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 Mount Hebron, CA?
On average, the last spring frost (32°F) around Mount Hebron, CA is about Jun 6. In cooler years it can run later, so for a safer bet many gardeners wait until May 16.
When is the first frost in the fall?
The first fall frost around Mount Hebron, CA typically arrives about Sep 28. 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 Jun 6 on average, or May 16 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 113 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 96058 Planting calendar → California frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026