Last spring frost
Mar 30
Frost Dates for Issaquah, WA
First fall frost
Nov 7
Growing season
223 days
Hardiness zone
8b
In an average year around Issaquah, WA, the last spring frost (32°F) is about Mar 30 and the first fall frost is about Nov 7, giving roughly a 223-day growing season. To be safe most years, wait until Mar 4 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 13 | Apr 26 | Apr 8 |
| Freeze (32°F) | Apr 21 | Mar 30 | Mar 4 |
| Hard (28°F) | Mar 25 | Feb 27 | Jan 16 |
| Severe (24°F) | Feb 28 | Jan 31 | Dec 6 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | May 13 | May 7 | May 2 | Apr 29 | Apr 26 | Apr 22 | Apr 18 | Apr 14 | Apr 8 |
| 32°F | Apr 21 | Apr 13 | Apr 8 | Apr 3 | Mar 30 | Mar 25 | Mar 20 | Mar 13 | Mar 4 |
| 28°F | Mar 25 | Mar 17 | Mar 9 | Mar 2 | Feb 27 | Feb 22 | Feb 15 | Feb 6 | Jan 16 |
| 24°F | Feb 28 | Feb 24 | Feb 17 | Feb 9 | Jan 31 | Jan 18 | Jan 4 | Dec 22 | Dec 6 |
| 20°F | Feb 25 | Feb 18 | Feb 6 | Jan 26 | Jan 8 | Dec 31 | Dec 19 | Dec 8 | 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) | Oct 4 | Oct 22 | Nov 7 |
| Freeze (32°F) | Oct 22 | Nov 7 | Dec 1 |
| Hard (28°F) | Nov 6 | Nov 29 | Dec 31 |
| Severe (24°F) | Nov 21 | Dec 18 | Feb 6 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Oct 4 | Oct 10 | Oct 14 | Oct 18 | Oct 22 | Oct 25 | Oct 29 | Nov 1 | Nov 7 |
| 32°F | Oct 22 | Oct 28 | Nov 1 | Nov 3 | Nov 7 | Nov 11 | Nov 17 | Nov 24 | Dec 1 |
| 28°F | Nov 6 | Nov 12 | Nov 19 | Nov 25 | Nov 29 | Dec 4 | Dec 11 | Dec 19 | Dec 31 |
| 24°F | Nov 21 | Nov 28 | Dec 5 | Dec 11 | Dec 18 | Dec 27 | Jan 3 | Jan 14 | Feb 6 |
| 20°F | Nov 28 | Dec 4 | Dec 9 | Dec 17 | Dec 28 | Jan 4 | Jan 14 | Feb 3 | Feb 21 |
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: Snoqualmie Falls, Wa, about 7.6 miles away@if(!empty($station['elevation_ft'])), at 440 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 Issaquah, WA?
On average, the last spring frost (32°F) around Issaquah, WA is about Mar 30. In cooler years it can run later, so for a safer bet many gardeners wait until Mar 4.
When is the first frost in the fall?
The first fall frost around Issaquah, WA typically arrives about Nov 7. 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 30 on average, or Mar 4 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 223 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 98027 Planting calendar → Washington frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026