Last spring frost
Apr 7
Frost Dates for South Prairie, WA
First fall frost
Oct 30
Growing season
204 days
Hardiness zone
8b
In an average year around South Prairie, WA, the last spring frost (32°F) is about Apr 7 and the first fall frost is about Oct 30, giving roughly a 204-day growing season. To be safe most years, wait until Mar 16 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 19 | May 1 | Apr 15 |
| Freeze (32°F) | Apr 27 | Apr 7 | Mar 16 |
| Hard (28°F) | Mar 31 | Mar 8 | Feb 11 |
| Severe (24°F) | Mar 8 | Feb 8 | Dec 26 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | May 19 | May 12 | May 8 | May 4 | May 1 | Apr 29 | Apr 25 | Apr 21 | Apr 15 |
| 32°F | Apr 27 | Apr 20 | Apr 15 | Apr 11 | Apr 7 | Apr 3 | Mar 30 | Mar 26 | Mar 16 |
| 28°F | Mar 31 | Mar 25 | Mar 19 | Mar 13 | Mar 8 | Mar 2 | Feb 27 | Feb 21 | Feb 11 |
| 24°F | Mar 8 | Feb 28 | Feb 22 | Feb 16 | Feb 8 | Jan 31 | Jan 20 | Jan 7 | Dec 26 |
| 20°F | Feb 23 | Feb 13 | Jan 31 | Jan 21 | Jan 12 | Jan 4 | Dec 28 | Dec 14 | Dec 4 |
| 16°F | Feb 12 | Jan 30 | Jan 16 | Jan 6 | Jan 1 | Dec 25 | Dec 16 | Dec 9 | Dec 1 |
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 28 | Oct 11 | Oct 31 |
| Freeze (32°F) | Oct 8 | Oct 30 | Nov 22 |
| Hard (28°F) | Oct 26 | Nov 21 | Dec 15 |
| Severe (24°F) | Nov 11 | Dec 8 | Jan 13 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 28 | Oct 2 | Oct 5 | Oct 8 | Oct 11 | Oct 15 | Oct 18 | Oct 23 | Oct 31 |
| 32°F | Oct 8 | Oct 16 | Oct 20 | Oct 25 | Oct 30 | Nov 2 | Nov 7 | Nov 13 | Nov 22 |
| 28°F | Oct 26 | Nov 2 | Nov 9 | Nov 14 | Nov 21 | Nov 25 | Nov 29 | Dec 5 | Dec 15 |
| 24°F | Nov 11 | Nov 22 | Nov 29 | Dec 2 | Dec 8 | Dec 15 | Dec 22 | Dec 29 | Jan 13 |
| 20°F | Nov 26 | Dec 2 | Dec 7 | Dec 13 | Dec 21 | Dec 29 | Jan 4 | Jan 17 | Feb 5 |
| 16°F | Nov 30 | Dec 6 | Dec 10 | Dec 18 | Dec 27 | Jan 1 | Jan 6 | Jan 18 | Feb 4 |
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: Buckley 1 Ne, Wa, about 4.8 miles away@if(!empty($station['elevation_ft'])), at 685 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 South Prairie, WA?
On average, the last spring frost (32°F) around South Prairie, WA is about Apr 7. In cooler years it can run later, so for a safer bet many gardeners wait until Mar 16.
When is the first frost in the fall?
The first fall frost around South Prairie, WA typically arrives about Oct 30. 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 7 on average, or Mar 16 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 204 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 98385 Planting calendar → Washington frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026