Last spring frost
May 7
Frost Dates for Rosalia, WA
First fall frost
Sep 28
Growing season
144 days
Hardiness zone
6b
In an average year around Rosalia, WA, the last spring frost (32°F) is about May 7 and the first fall frost is about Sep 28, giving roughly a 144-day growing season. To be safe most years, wait until Apr 22 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 5 | May 31 | May 8 |
| Freeze (32°F) | May 25 | May 7 | Apr 22 |
| Hard (28°F) | May 8 | Apr 20 | Mar 25 |
| Severe (24°F) | Apr 20 | Mar 22 | Feb 28 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Jul 5 | Jun 23 | Jun 12 | Jun 5 | May 31 | May 27 | May 22 | May 16 | May 8 |
| 32°F | May 25 | May 19 | May 14 | May 10 | May 7 | May 4 | May 1 | Apr 27 | Apr 22 |
| 28°F | May 8 | May 3 | Apr 29 | Apr 25 | Apr 20 | Apr 16 | Apr 10 | Apr 1 | Mar 25 |
| 24°F | Apr 20 | Apr 10 | Apr 3 | Mar 29 | Mar 22 | Mar 16 | Mar 12 | Mar 7 | Feb 28 |
| 20°F | Mar 29 | Mar 17 | Mar 10 | Mar 5 | Mar 1 | Feb 26 | Feb 20 | Feb 12 | Feb 2 |
| 16°F | Mar 11 | Mar 3 | Feb 28 | Feb 22 | Feb 16 | Feb 9 | Feb 3 | Jan 27 | Jan 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) | Aug 26 | Sep 13 | Sep 28 |
| Freeze (32°F) | Sep 11 | Sep 28 | Oct 16 |
| Hard (28°F) | Sep 25 | Oct 12 | Nov 2 |
| Severe (24°F) | Oct 6 | Oct 28 | Nov 20 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Aug 26 | Sep 2 | Sep 5 | Sep 10 | Sep 13 | Sep 17 | Sep 21 | Sep 23 | Sep 28 |
| 32°F | Sep 11 | Sep 16 | Sep 21 | Sep 25 | Sep 28 | Oct 1 | Oct 4 | Oct 9 | Oct 16 |
| 28°F | Sep 25 | Oct 1 | Oct 4 | Oct 7 | Oct 12 | Oct 16 | Oct 20 | Oct 25 | Nov 2 |
| 24°F | Oct 6 | Oct 14 | Oct 20 | Oct 24 | Oct 28 | Oct 31 | Nov 3 | Nov 10 | Nov 20 |
| 20°F | Oct 21 | Oct 28 | Nov 1 | Nov 5 | Nov 10 | Nov 17 | Nov 23 | Nov 28 | Dec 5 |
| 16°F | Oct 31 | Nov 6 | Nov 13 | Nov 21 | Nov 27 | Dec 1 | Dec 7 | Dec 13 | Dec 23 |
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: Rosalia, Wa, about 2 miles away@if(!empty($station['elevation_ft'])), at 2,420 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 Rosalia, WA?
On average, the last spring frost (32°F) around Rosalia, WA is about May 7. In cooler years it can run later, so for a safer bet many gardeners wait until Apr 22.
When is the first frost in the fall?
The first fall frost around Rosalia, WA typically arrives about Sep 28. 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 7 on average, or Apr 22 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 144 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 99170 Planting calendar → Washington frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026