Last spring frost
Mar 13
Frost Dates for Seattle, WA
First fall frost
Nov 17
Growing season
247 days
Hardiness zone
9a
In an average year around Seattle, WA, the last spring frost (32°F) is about Mar 13 and the first fall frost is about Nov 17, giving roughly a 247-day growing season. To be safe most years, wait until Feb 20 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 28 | Apr 3 | Mar 17 |
| Freeze (32°F) | Apr 1 | Mar 13 | Feb 20 |
| Hard (28°F) | Mar 10 | Feb 18 | Jan 7 |
| Severe (24°F) | Feb 23 | Jan 17 | Dec 7 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 28 | Apr 20 | Apr 12 | Apr 7 | Apr 3 | Mar 31 | Mar 27 | Mar 23 | Mar 17 |
| 32°F | Apr 1 | Mar 25 | Mar 21 | Mar 17 | Mar 13 | Mar 9 | Mar 4 | Feb 28 | Feb 20 |
| 28°F | Mar 10 | Mar 3 | Feb 27 | Feb 22 | Feb 18 | Feb 11 | Feb 2 | Jan 22 | Jan 7 |
| 24°F | Feb 23 | Feb 17 | Feb 7 | Jan 31 | Jan 17 | Jan 6 | Dec 31 | Dec 18 | Dec 7 |
| 20°F | Feb 13 | Jan 31 | Jan 15 | Jan 1 | Dec 27 | Dec 18 | Dec 12 | Dec 7 | 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) | Oct 17 | Oct 31 | Nov 17 |
| Freeze (32°F) | Nov 1 | Nov 17 | Dec 6 |
| Hard (28°F) | Nov 12 | Dec 2 | Dec 30 |
| Severe (24°F) | Nov 21 | Dec 14 | Jan 29 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Oct 17 | Oct 22 | Oct 26 | Oct 29 | Oct 31 | Nov 3 | Nov 7 | Nov 11 | Nov 17 |
| 32°F | Nov 1 | Nov 6 | Nov 10 | Nov 13 | Nov 17 | Nov 21 | Nov 24 | Nov 29 | Dec 6 |
| 28°F | Nov 12 | Nov 18 | Nov 23 | Nov 27 | Dec 2 | Dec 7 | Dec 13 | Dec 20 | Dec 30 |
| 24°F | Nov 21 | Nov 29 | Dec 3 | Dec 8 | Dec 14 | Dec 21 | Dec 29 | Jan 7 | Jan 29 |
| 20°F | Nov 26 | Dec 1 | Dec 6 | Dec 12 | Dec 19 | Dec 25 | Jan 1 | Jan 14 | Feb 3 |
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 Boeing Fld, Wa, about 4.3 miles away@if(!empty($station['elevation_ft'])), at 20 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 13. In cooler years it can run later, so for a safer bet many gardeners wait until Feb 20.
When is the first frost in the fall?
The first fall frost around Seattle, WA typically arrives about Nov 17. 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 13 on average, or Feb 20 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 247 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 98136 Planting calendar → Washington frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026