Last spring frost
Apr 24
Frost Dates for Morton, WA
First fall frost
Oct 15
Growing season
176 days
Hardiness zone
8a
In an average year around Morton, WA, the last spring frost (32°F) is about Apr 24 and the first fall frost is about Oct 15, giving roughly a 176-day growing season. To be safe most years, wait until Mar 31 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 31 | May 13 | Apr 27 |
| Freeze (32°F) | May 12 | Apr 24 | Mar 31 |
| Hard (28°F) | Apr 18 | Mar 26 | Feb 27 |
| Severe (24°F) | Mar 19 | Feb 22 | Jan 17 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | May 31 | May 25 | May 20 | May 17 | May 13 | May 9 | May 5 | May 1 | Apr 27 |
| 32°F | May 12 | May 5 | May 1 | Apr 28 | Apr 24 | Apr 19 | Apr 15 | Apr 9 | Mar 31 |
| 28°F | Apr 18 | Apr 10 | Apr 5 | Mar 31 | Mar 26 | Mar 20 | Mar 12 | Mar 5 | Feb 27 |
| 24°F | Mar 19 | Mar 8 | Mar 1 | Feb 26 | Feb 22 | Feb 17 | Feb 12 | Jan 31 | Jan 17 |
| 20°F | Feb 28 | Feb 21 | Feb 16 | Feb 10 | Jan 31 | Jan 24 | Jan 13 | Jan 3 | Dec 16 |
| 16°F | Feb 20 | Feb 12 | Feb 3 | Jan 23 | Jan 13 | Jan 1 | Dec 23 | Dec 10 | Nov 30 |
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 5 | Sep 25 | Oct 16 |
| Freeze (32°F) | Sep 24 | Oct 15 | Nov 8 |
| Hard (28°F) | Oct 13 | Nov 5 | Nov 26 |
| Severe (24°F) | Oct 30 | Nov 22 | Dec 26 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 5 | Sep 10 | Sep 15 | Sep 20 | Sep 25 | Sep 29 | Oct 2 | Oct 7 | Oct 16 |
| 32°F | Sep 24 | Oct 1 | Oct 5 | Oct 12 | Oct 15 | Oct 20 | Oct 25 | Nov 1 | Nov 8 |
| 28°F | Oct 13 | Oct 21 | Oct 27 | Nov 1 | Nov 5 | Nov 9 | Nov 13 | Nov 18 | Nov 26 |
| 24°F | Oct 30 | Nov 6 | Nov 11 | Nov 16 | Nov 22 | Nov 28 | Dec 4 | Dec 14 | Dec 26 |
| 20°F | Nov 12 | Nov 23 | Nov 30 | Dec 5 | Dec 12 | Dec 22 | Jan 1 | Jan 12 | Jan 26 |
| 16°F | Nov 22 | Dec 2 | Dec 8 | Dec 16 | Dec 27 | Jan 4 | Jan 17 | Jan 31 | Feb 14 |
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: Glenoma, Wa, about 6.2 miles away@if(!empty($station['elevation_ft'])), at 840 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 Morton, WA?
On average, the last spring frost (32°F) around Morton, WA is about Apr 24. In cooler years it can run later, so for a safer bet many gardeners wait until Mar 31.
When is the first frost in the fall?
The first fall frost around Morton, WA typically arrives about Oct 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 Apr 24 on average, or Mar 31 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 176 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 98336 Planting calendar → Washington frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026