Last spring frost
Mar 14
Frost Dates for North Bonneville, WA
First fall frost
Nov 27
Growing season
257 days
Hardiness zone
9a
In an average year around North Bonneville, WA, the last spring frost (32°F) is about Mar 14 and the first fall frost is about Nov 27, giving roughly a 257-day growing season. To be safe most years, wait until Feb 19 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 5 | Apr 15 | Mar 23 |
| Freeze (32°F) | Apr 4 | Mar 14 | Feb 19 |
| Hard (28°F) | Mar 10 | Feb 14 | Jan 4 |
| Severe (24°F) | Feb 26 | Jan 21 | Dec 17 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | May 5 | Apr 30 | Apr 25 | Apr 20 | Apr 15 | Apr 10 | Apr 4 | Mar 31 | Mar 23 |
| 32°F | Apr 4 | Mar 28 | Mar 24 | Mar 19 | Mar 14 | Mar 10 | Mar 5 | Feb 28 | Feb 19 |
| 28°F | Mar 10 | Mar 2 | Feb 25 | Feb 19 | Feb 14 | Feb 7 | Jan 28 | Jan 14 | Jan 4 |
| 24°F | Feb 26 | Feb 18 | Feb 11 | Jan 31 | Jan 21 | Jan 10 | Jan 6 | Dec 31 | Dec 17 |
| 20°F | Feb 21 | Feb 12 | Jan 30 | Jan 18 | Jan 9 | Jan 6 | Dec 31 | Dec 21 | Dec 11 |
| 16°F | Feb 13 | Feb 6 | Jan 24 | Jan 13 | Jan 7 | Jan 3 | Dec 29 | Dec 23 | Dec 13 |
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 10 | Nov 27 |
| Freeze (32°F) | Nov 8 | Nov 27 | Dec 15 |
| Hard (28°F) | Nov 21 | Dec 14 | Jan 13 |
| Severe (24°F) | Dec 1 | Dec 30 | Feb 10 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Oct 24 | Oct 30 | Nov 2 | Nov 6 | Nov 10 | Nov 12 | Nov 16 | Nov 21 | Nov 27 |
| 32°F | Nov 8 | Nov 13 | Nov 18 | Nov 23 | Nov 27 | Dec 1 | Dec 4 | Dec 8 | Dec 15 |
| 28°F | Nov 21 | Nov 29 | Dec 5 | Dec 9 | Dec 14 | Dec 20 | Dec 27 | Jan 2 | Jan 13 |
| 24°F | Dec 1 | Dec 10 | Dec 16 | Dec 24 | Dec 30 | Jan 3 | Jan 9 | Jan 21 | Feb 10 |
| 20°F | Dec 7 | Dec 13 | Dec 21 | Dec 29 | Jan 3 | Jan 7 | Jan 15 | Jan 30 | Feb 16 |
| 16°F | Dec 11 | Dec 17 | Dec 27 | Dec 30 | Jan 4 | Jan 7 | Jan 17 | Feb 1 | Feb 11 |
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: Bonneville Dam, Or, about 0.8 miles away@if(!empty($station['elevation_ft'])), at 62 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 North Bonneville, WA?
On average, the last spring frost (32°F) around North Bonneville, WA is about Mar 14. In cooler years it can run later, so for a safer bet many gardeners wait until Feb 19.
When is the first frost in the fall?
The first fall frost around North Bonneville, WA typically arrives about Nov 27. 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 14 on average, or Feb 19 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 257 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 98639 Planting calendar → Washington frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026