Last spring frost
Apr 8
Frost Dates for Upper Lake, CA
First fall frost
Nov 6
Growing season
211 days
Hardiness zone
9a
In an average year around Upper Lake, CA, the last spring frost (32°F) is about Apr 8 and the first fall frost is about Nov 6, giving roughly a 211-day growing season. To be safe most years, wait until Mar 11 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 25 | May 2 | Apr 15 |
| Freeze (32°F) | Apr 29 | Apr 8 | Mar 11 |
| Hard (28°F) | Apr 2 | Feb 28 | Jan 25 |
| Severe (24°F) | Feb 28 | Jan 26 | Dec 17 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | May 25 | May 17 | May 11 | May 6 | May 2 | Apr 29 | Apr 25 | Apr 21 | Apr 15 |
| 32°F | Apr 29 | Apr 22 | Apr 17 | Apr 12 | Apr 8 | Apr 4 | Mar 29 | Mar 22 | Mar 11 |
| 28°F | Apr 2 | Mar 21 | Mar 11 | Mar 4 | Feb 28 | Feb 23 | Feb 17 | Feb 8 | Jan 25 |
| 24°F | Feb 28 | Feb 20 | Feb 11 | Feb 1 | Jan 26 | Jan 15 | Jan 4 | Dec 27 | Dec 17 |
| 20°F | Jan 30 | Jan 21 | Jan 12 | Jan 4 | Jan 1 | Dec 28 | Dec 22 | Dec 16 | Dec 8 |
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 2 | Oct 21 | Nov 6 |
| Freeze (32°F) | Oct 20 | Nov 6 | Nov 24 |
| Hard (28°F) | Nov 3 | Nov 22 | Dec 12 |
| Severe (24°F) | Nov 17 | Dec 7 | Jan 5 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Oct 2 | Oct 8 | Oct 13 | Oct 17 | Oct 21 | Oct 26 | Oct 31 | Nov 3 | Nov 6 |
| 32°F | Oct 20 | Oct 27 | Nov 1 | Nov 3 | Nov 6 | Nov 9 | Nov 12 | Nov 17 | Nov 24 |
| 28°F | Nov 3 | Nov 8 | Nov 13 | Nov 18 | Nov 22 | Nov 26 | Dec 1 | Dec 4 | Dec 12 |
| 24°F | Nov 17 | Nov 25 | Nov 30 | Dec 3 | Dec 7 | Dec 12 | Dec 18 | Dec 29 | Jan 5 |
| 20°F | Dec 1 | Dec 4 | Dec 10 | Dec 16 | Dec 20 | Dec 28 | Jan 2 | Jan 6 | Jan 17 |
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: Potter Valley Powerhouse, Ca, about 15.2 miles away@if(!empty($station['elevation_ft'])), at 1,018 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 Upper Lake, CA?
On average, the last spring frost (32°F) around Upper Lake, CA is about Apr 8. In cooler years it can run later, so for a safer bet many gardeners wait until Mar 11.
When is the first frost in the fall?
The first fall frost around Upper Lake, CA typically arrives about Nov 6. 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 8 on average, or Mar 11 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 211 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 95485 Planting calendar → California frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026