Last spring frost
May 7
Frost Dates for Ritzville, WA
First fall frost
Oct 10
Growing season
153 days
Hardiness zone
6b
In an average year around Ritzville, WA, the last spring frost (32°F) is about May 7 and the first fall frost is about Oct 10, giving roughly a 153-day growing season. To be safe most years, wait until Apr 25 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) | Jun 16 | May 28 | May 8 |
| Freeze (32°F) | May 27 | May 7 | Apr 25 |
| Hard (28°F) | May 10 | Apr 25 | Apr 2 |
| Severe (24°F) | Apr 28 | Mar 30 | Mar 2 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Jun 16 | Jun 9 | Jun 4 | May 31 | May 28 | May 24 | May 18 | May 14 | May 8 |
| 32°F | May 27 | May 18 | May 13 | May 10 | May 7 | May 4 | May 1 | Apr 29 | Apr 25 |
| 28°F | May 10 | May 4 | May 1 | Apr 28 | Apr 25 | Apr 21 | Apr 17 | Apr 11 | Apr 2 |
| 24°F | Apr 28 | Apr 20 | Apr 11 | Apr 4 | Mar 30 | Mar 21 | Mar 14 | Mar 8 | Mar 2 |
| 20°F | Mar 29 | Mar 15 | Mar 10 | Mar 5 | Mar 1 | Feb 26 | Feb 20 | Feb 11 | Feb 1 |
| 16°F | Mar 7 | Mar 1 | Feb 24 | Feb 16 | Feb 8 | Feb 2 | Jan 26 | Jan 14 | Jan 3 |
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) | Sep 10 | Sep 28 | Oct 12 |
| Freeze (32°F) | Sep 27 | Oct 10 | Oct 25 |
| Hard (28°F) | Oct 4 | Oct 21 | Nov 6 |
| Severe (24°F) | Oct 16 | Nov 1 | Nov 21 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 10 | Sep 16 | Sep 21 | Sep 24 | Sep 28 | Oct 1 | Oct 4 | Oct 7 | Oct 12 |
| 32°F | Sep 27 | Oct 1 | Oct 4 | Oct 6 | Oct 10 | Oct 12 | Oct 15 | Oct 19 | Oct 25 |
| 28°F | Oct 4 | Oct 10 | Oct 15 | Oct 18 | Oct 21 | Oct 24 | Oct 27 | Nov 1 | Nov 6 |
| 24°F | Oct 16 | Oct 22 | Oct 26 | Oct 30 | Nov 1 | Nov 6 | Nov 9 | Nov 14 | Nov 21 |
| 20°F | Oct 25 | Nov 1 | Nov 6 | Nov 11 | Nov 15 | Nov 19 | Nov 24 | Nov 28 | Dec 5 |
| 16°F | Nov 6 | Nov 14 | Nov 20 | Nov 25 | Nov 29 | Dec 3 | Dec 9 | Dec 16 | Dec 26 |
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: Ritzville 1 Sse, Wa, about 0.4 miles away@if(!empty($station['elevation_ft'])), at 1,864 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 Ritzville, WA?
On average, the last spring frost (32°F) around Ritzville, WA is about May 7. In cooler years it can run later, so for a safer bet many gardeners wait until Apr 25.
When is the first frost in the fall?
The first fall frost around Ritzville, WA typically arrives about Oct 10. 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 25 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 153 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 99169 Planting calendar → Washington frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026