Last spring frost
May 16
Frost Dates for Twin Lakes, WA
First fall frost
Sep 15
Growing season
120 days
Hardiness zone
6b
In an average year around Twin Lakes, WA, the last spring frost (32°F) is about May 16 and the first fall frost is about Sep 15, giving roughly a 120-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%) |
|---|---|---|---|
| Freeze (32°F) | Jun 7 | May 16 | Apr 30 |
| Hard (28°F) | May 14 | Apr 30 | Apr 12 |
| Severe (24°F) | Apr 30 | Apr 8 | Mar 17 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 32°F | Jun 7 | May 31 | May 25 | May 20 | May 16 | May 12 | May 9 | May 5 | Apr 30 |
| 28°F | May 14 | May 8 | May 5 | May 1 | Apr 30 | Apr 27 | Apr 23 | Apr 18 | Apr 12 |
| 24°F | Apr 30 | Apr 24 | Apr 18 | Apr 14 | Apr 8 | Apr 3 | Mar 31 | Mar 25 | Mar 17 |
| 20°F | Apr 8 | Mar 31 | Mar 27 | Mar 21 | Mar 16 | Mar 13 | Mar 10 | Mar 6 | Mar 1 |
| 16°F | Mar 17 | Mar 12 | Mar 9 | Mar 6 | Mar 3 | Feb 28 | Feb 25 | Feb 21 | Feb 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%) |
|---|---|---|---|
| Freeze (32°F) | Sep 1 | Sep 15 | Sep 29 |
| Hard (28°F) | Sep 15 | Sep 28 | Oct 13 |
| Severe (24°F) | Sep 28 | Oct 10 | Oct 28 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 32°F | Sep 1 | Sep 5 | Sep 8 | Sep 12 | Sep 15 | Sep 18 | Sep 21 | Sep 24 | Sep 29 |
| 28°F | Sep 15 | Sep 19 | Sep 22 | Sep 26 | Sep 28 | Oct 1 | Oct 3 | Oct 7 | Oct 13 |
| 24°F | Sep 28 | Oct 1 | Oct 3 | Oct 6 | Oct 10 | Oct 13 | Oct 17 | Oct 22 | Oct 28 |
| 20°F | Oct 5 | Oct 10 | Oct 16 | Oct 20 | Oct 24 | Oct 29 | Nov 1 | Nov 6 | Nov 17 |
| 16°F | Oct 15 | Oct 24 | Oct 30 | Nov 3 | Nov 9 | Nov 14 | Nov 21 | Nov 28 | Dec 7 |
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: Chewelah, Wa, about 30 miles away@if(!empty($station['elevation_ft'])), at 1,670 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 Twin Lakes, WA?
On average, the last spring frost (32°F) around Twin Lakes, WA is about May 16. 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 Twin Lakes, WA typically arrives about Sep 15. 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 16 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 120 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 99138 Planting calendar → Washington frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026