Last spring frost
May 18
Frost Dates for Trout Lake, WA
First fall frost
Sep 25
Growing season
125 days
Hardiness zone
7a
In an average year around Trout Lake, WA, the last spring frost (32°F) is about May 18 and the first fall frost is about Sep 25, giving roughly a 125-day growing season. To be safe most years, wait until May 1 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 2 | Jun 13 | May 23 |
| Freeze (32°F) | Jun 12 | May 18 | May 1 |
| Hard (28°F) | May 16 | Apr 29 | Apr 11 |
| Severe (24°F) | Apr 28 | Apr 1 | Mar 8 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Jul 2 | Jun 26 | Jun 21 | Jun 17 | Jun 13 | Jun 9 | Jun 4 | May 31 | May 23 |
| 32°F | Jun 12 | Jun 3 | May 29 | May 22 | May 18 | May 14 | May 10 | May 7 | May 1 |
| 28°F | May 16 | May 9 | May 5 | May 2 | Apr 29 | Apr 27 | Apr 23 | Apr 18 | Apr 11 |
| 24°F | Apr 28 | Apr 19 | Apr 12 | Apr 6 | Apr 1 | Mar 27 | Mar 22 | Mar 15 | Mar 8 |
| 20°F | Mar 31 | Mar 18 | Mar 12 | Mar 6 | Mar 2 | Feb 27 | Feb 23 | Feb 17 | Feb 6 |
| 16°F | Mar 9 | Mar 2 | Feb 25 | Feb 19 | Feb 15 | Feb 8 | Feb 1 | Jan 18 | Jan 5 |
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 20 | Sep 7 | Sep 25 |
| Freeze (32°F) | Sep 4 | Sep 25 | Oct 10 |
| Hard (28°F) | Sep 21 | Oct 9 | Nov 1 |
| Severe (24°F) | Oct 5 | Oct 27 | Nov 18 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Aug 20 | Aug 29 | Sep 1 | Sep 4 | Sep 7 | Sep 10 | Sep 14 | Sep 19 | Sep 25 |
| 32°F | Sep 4 | Sep 11 | Sep 16 | Sep 21 | Sep 25 | Sep 28 | Oct 1 | Oct 4 | Oct 10 |
| 28°F | Sep 21 | Sep 29 | Oct 2 | Oct 5 | Oct 9 | Oct 13 | Oct 17 | Oct 23 | Nov 1 |
| 24°F | Oct 5 | Oct 13 | Oct 18 | Oct 23 | Oct 27 | Nov 1 | Nov 5 | Nov 11 | Nov 18 |
| 20°F | Oct 19 | Oct 29 | Nov 3 | Nov 11 | Nov 16 | Nov 20 | Nov 25 | Dec 1 | Dec 10 |
| 16°F | Nov 3 | Nov 14 | Nov 22 | Nov 27 | Dec 1 | Dec 5 | Dec 11 | Dec 21 | Jan 3 |
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: Mt Adams Rs, Wa, about 3.7 miles away@if(!empty($station['elevation_ft'])), at 1,950 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 Trout Lake, WA?
On average, the last spring frost (32°F) around Trout Lake, WA is about May 18. In cooler years it can run later, so for a safer bet many gardeners wait until May 1.
When is the first frost in the fall?
The first fall frost around Trout Lake, WA typically arrives about Sep 25. 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 18 on average, or May 1 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 125 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 98650 Planting calendar → Washington frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026