Last spring frost
Mar 8
Frost Dates for Seattle, WA
First fall frost
Nov 23
Growing season
259 days
Hardiness zone
9a
In an average year around Seattle, WA, the last spring frost (32°F) is about Mar 8 and the first fall frost is about Nov 23, giving roughly a 259-day growing season. To be safe most years, wait until Feb 13 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) | Apr 26 | Apr 4 | Mar 17 |
| Freeze (32°F) | Mar 29 | Mar 8 | Feb 13 |
| Hard (28°F) | Mar 1 | Feb 11 | Dec 27 |
| Severe (24°F) | Feb 20 | Jan 9 | Dec 3 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 26 | Apr 18 | Apr 12 | Apr 7 | Apr 4 | Apr 1 | Mar 28 | Mar 23 | Mar 17 |
| 32°F | Mar 29 | Mar 21 | Mar 16 | Mar 11 | Mar 8 | Mar 3 | Feb 27 | Feb 23 | Feb 13 |
| 28°F | Mar 1 | Feb 25 | Feb 21 | Feb 16 | Feb 11 | Feb 2 | Jan 24 | Jan 9 | Dec 27 |
| 24°F | Feb 20 | Feb 11 | Feb 3 | Jan 24 | Jan 9 | Jan 1 | Dec 22 | Dec 12 | Dec 3 |
| 20°F | Feb 13 | Jan 31 | Jan 6 | Dec 30 | Dec 23 | Dec 15 | Dec 11 | Dec 5 | Nov 29 |
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) | Oct 24 | Nov 5 | Nov 22 |
| Freeze (32°F) | Nov 4 | Nov 23 | Dec 16 |
| Hard (28°F) | Nov 17 | Dec 11 | Jan 17 |
| Severe (24°F) | Nov 27 | Dec 24 | Feb 8 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Oct 24 | Oct 28 | Oct 31 | Nov 2 | Nov 5 | Nov 8 | Nov 12 | Nov 16 | Nov 22 |
| 32°F | Nov 4 | Nov 10 | Nov 15 | Nov 19 | Nov 23 | Nov 27 | Dec 1 | Dec 6 | Dec 16 |
| 28°F | Nov 17 | Nov 25 | Dec 1 | Dec 5 | Dec 11 | Dec 16 | Dec 24 | Jan 1 | Jan 17 |
| 24°F | Nov 27 | Dec 2 | Dec 9 | Dec 15 | Dec 24 | Jan 1 | Jan 8 | Jan 24 | Feb 8 |
| 20°F | Nov 28 | Dec 4 | Dec 9 | Dec 14 | Dec 20 | Dec 27 | Jan 5 | Jan 28 | Feb 10 |
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: Seattle Sand Pt Wsfo, Wa, about 6.1 miles away@if(!empty($station['elevation_ft'])), at 60 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 Seattle, WA?
On average, the last spring frost (32°F) around Seattle, WA is about Mar 8. In cooler years it can run later, so for a safer bet many gardeners wait until Feb 13.
When is the first frost in the fall?
The first fall frost around Seattle, WA typically arrives about Nov 23. 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 Mar 8 on average, or Feb 13 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 259 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 98117 Planting calendar → Washington frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026