Last spring frost
May 22
Frost Dates for Alta, CA
First fall frost
Oct 16
Growing season
147 days
Hardiness zone
8a
In an average year around Alta, CA, the last spring frost (32°F) is about May 22 and the first fall frost is about Oct 16, giving roughly a 147-day growing season. To be safe most years, wait until Apr 30 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) | Jun 28 | Jun 10 | May 24 |
| Freeze (32°F) | Jun 8 | May 22 | Apr 30 |
| Hard (28°F) | May 21 | Apr 30 | Apr 13 |
| Severe (24°F) | May 1 | Apr 13 | Mar 22 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Jun 28 | Jun 21 | Jun 17 | Jun 13 | Jun 10 | Jun 7 | Jun 4 | Jun 1 | May 24 |
| 32°F | Jun 8 | Jun 2 | May 30 | May 26 | May 22 | May 17 | May 13 | May 7 | Apr 30 |
| 28°F | May 21 | May 13 | May 8 | May 3 | Apr 30 | Apr 27 | Apr 23 | Apr 18 | Apr 13 |
| 24°F | May 1 | Apr 25 | Apr 20 | Apr 16 | Apr 13 | Apr 9 | Apr 6 | Apr 1 | Mar 22 |
| 20°F | Apr 16 | Apr 10 | Apr 5 | Mar 31 | Mar 24 | Mar 17 | Mar 10 | Mar 2 | Feb 19 |
| 16°F | Apr 5 | Mar 25 | Mar 14 | Mar 6 | Feb 28 | Feb 18 | Feb 4 | Jan 21 | Jan 2 |
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) | Sep 8 | Sep 27 | Oct 15 |
| Freeze (32°F) | Sep 26 | Oct 16 | Nov 3 |
| Hard (28°F) | Oct 15 | Nov 3 | Nov 18 |
| Severe (24°F) | Nov 1 | Nov 19 | Dec 4 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 8 | Sep 13 | Sep 18 | Sep 23 | Sep 27 | Sep 30 | Oct 4 | Oct 8 | Oct 15 |
| 32°F | Sep 26 | Oct 2 | Oct 7 | Oct 12 | Oct 16 | Oct 20 | Oct 25 | Oct 30 | Nov 3 |
| 28°F | Oct 15 | Oct 23 | Oct 28 | Oct 31 | Nov 3 | Nov 6 | Nov 9 | Nov 13 | Nov 18 |
| 24°F | Nov 1 | Nov 6 | Nov 11 | Nov 15 | Nov 19 | Nov 22 | Nov 25 | Nov 29 | Dec 4 |
| 20°F | Nov 14 | Nov 19 | Nov 24 | Nov 28 | Dec 1 | Dec 5 | Dec 9 | Dec 14 | Dec 23 |
| 16°F | Nov 24 | Dec 1 | Dec 5 | Dec 10 | Dec 15 | Dec 21 | Dec 28 | Jan 8 | Jan 25 |
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: Lake Spaulding, Ca, about 2.9 miles away@if(!empty($station['elevation_ft'])), at 5,156 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 Alta, CA?
On average, the last spring frost (32°F) around Alta, CA is about May 22. In cooler years it can run later, so for a safer bet many gardeners wait until Apr 30.
When is the first frost in the fall?
The first fall frost around Alta, CA typically arrives about Oct 16. 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 May 22 on average, or Apr 30 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 147 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 95715 Planting calendar → California frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026