Last spring frost
Apr 14
Frost Dates for Grass Valley, CA
First fall frost
Nov 20
Growing season
218 days
Hardiness zone
9a
In an average year around Grass Valley, CA, the last spring frost (32°F) is about Apr 14 and the first fall frost is about Nov 20, giving roughly a 218-day growing season. To be safe most years, wait until Mar 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%) |
|---|---|---|---|
| Light (36°F) | May 23 | Apr 30 | Apr 12 |
| Freeze (32°F) | May 7 | Apr 14 | Mar 15 |
| Hard (28°F) | Apr 18 | Mar 17 | Jan 24 |
| Severe (24°F) | Apr 1 | Jan 24 | Dec 13 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | May 23 | May 14 | May 8 | May 3 | Apr 30 | Apr 27 | Apr 23 | Apr 19 | Apr 12 |
| 32°F | May 7 | Apr 29 | Apr 23 | Apr 19 | Apr 14 | Apr 9 | Apr 4 | Mar 28 | Mar 15 |
| 28°F | Apr 18 | Apr 9 | Apr 4 | Mar 27 | Mar 17 | Mar 7 | Feb 27 | Feb 13 | Jan 24 |
| 24°F | Apr 1 | Feb 28 | Feb 18 | Feb 6 | Jan 24 | Jan 12 | Jan 2 | Dec 27 | Dec 13 |
| 20°F | Jan 31 | Jan 18 | Jan 9 | Jan 4 | Jan 1 | Dec 29 | Dec 23 | Dec 18 | Dec 12 |
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 10 | Nov 2 | Nov 21 |
| Freeze (32°F) | Oct 23 | Nov 20 | Dec 12 |
| Hard (28°F) | Nov 12 | Dec 8 | Jan 19 |
| Severe (24°F) | Nov 27 | Dec 27 | Feb 21 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Oct 10 | Oct 17 | Oct 24 | Oct 29 | Nov 2 | Nov 6 | Nov 10 | Nov 15 | Nov 21 |
| 32°F | Oct 23 | Nov 3 | Nov 10 | Nov 16 | Nov 20 | Nov 25 | Nov 30 | Dec 4 | Dec 12 |
| 28°F | Nov 12 | Nov 22 | Nov 29 | Dec 3 | Dec 8 | Dec 13 | Dec 19 | Dec 31 | Jan 19 |
| 24°F | Nov 27 | Dec 6 | Dec 15 | Dec 20 | Dec 27 | Jan 2 | Jan 13 | Jan 27 | Feb 21 |
| 20°F | Dec 9 | Dec 16 | Dec 21 | Dec 26 | Dec 30 | Jan 1 | Jan 6 | Jan 16 | Jan 29 |
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: Nevada City, Ca, about 3.9 miles away@if(!empty($station['elevation_ft'])), at 2,781 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 Grass Valley, CA?
On average, the last spring frost (32°F) around Grass Valley, CA is about Apr 14. In cooler years it can run later, so for a safer bet many gardeners wait until Mar 15.
When is the first frost in the fall?
The first fall frost around Grass Valley, CA typically arrives about Nov 20. 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 14 on average, or Mar 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 218 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 95945 Planting calendar → California frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026