Last spring frost
Jun 3
Frost Dates for Alturas, CA
First fall frost
Sep 13
Growing season
97 days
Hardiness zone
6b
In an average year around Alturas, CA, the last spring frost (32°F) is about Jun 3 and the first fall frost is about Sep 13, giving roughly a 97-day growing season. To be safe most years, wait until May 15 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%) |
|---|---|---|---|
| Freeze (32°F) | Jun 26 | Jun 3 | May 15 |
| Hard (28°F) | Jun 5 | May 14 | Apr 26 |
| Severe (24°F) | May 16 | Apr 25 | Apr 4 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 32°F | Jun 26 | Jun 18 | Jun 12 | Jun 7 | Jun 3 | May 31 | May 27 | May 22 | May 15 |
| 28°F | Jun 5 | May 30 | May 23 | May 18 | May 14 | May 10 | May 5 | Apr 30 | Apr 26 |
| 24°F | May 16 | May 8 | May 2 | Apr 29 | Apr 25 | Apr 21 | Apr 17 | Apr 11 | Apr 4 |
| 20°F | Apr 29 | Apr 21 | Apr 14 | Apr 9 | Apr 5 | Apr 1 | Mar 27 | Mar 20 | Mar 12 |
| 16°F | Apr 11 | Apr 3 | Mar 27 | Mar 20 | Mar 14 | Mar 8 | Mar 2 | Feb 25 | Feb 16 |
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%) |
|---|---|---|---|
| Freeze (32°F) | Aug 27 | Sep 13 | Sep 28 |
| Hard (28°F) | Sep 11 | Sep 27 | Oct 16 |
| Severe (24°F) | Sep 27 | Oct 13 | Nov 1 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 32°F | Aug 27 | Sep 3 | Sep 6 | Sep 10 | Sep 13 | Sep 16 | Sep 19 | Sep 23 | Sep 28 |
| 28°F | Sep 11 | Sep 17 | Sep 21 | Sep 24 | Sep 27 | Sep 30 | Oct 3 | Oct 7 | Oct 16 |
| 24°F | Sep 27 | Oct 1 | Oct 4 | Oct 8 | Oct 13 | Oct 17 | Oct 22 | Oct 27 | Nov 1 |
| 20°F | Oct 9 | Oct 16 | Oct 21 | Oct 26 | Oct 30 | Nov 1 | Nov 4 | Nov 8 | Nov 16 |
| 16°F | Oct 21 | Oct 28 | Nov 1 | Nov 4 | Nov 8 | Nov 12 | Nov 16 | Nov 23 | Dec 1 |
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: Alturas, Ca, about 2.9 miles away@if(!empty($station['elevation_ft'])), at 4,378 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 Alturas, CA?
On average, the last spring frost (32°F) around Alturas, CA is about Jun 3. In cooler years it can run later, so for a safer bet many gardeners wait until May 15.
When is the first frost in the fall?
The first fall frost around Alturas, CA typically arrives about Sep 13. 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 3 on average, or May 15 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 97 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 96101 Planting calendar → California frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026