Last spring frost
Mar 18
Frost Dates for Wilsonville, OR
First fall frost
Nov 13
Growing season
243 days
Hardiness zone
8b
In an average year around Wilsonville, OR, the last spring frost (32°F) is about Mar 18 and the first fall frost is about Nov 13, giving roughly a 243-day growing season. To be safe most years, wait until Feb 22 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 6 | Apr 17 | Mar 29 |
| Freeze (32°F) | Apr 10 | Mar 18 | Feb 22 |
| Hard (28°F) | Mar 10 | Feb 13 | Dec 30 |
| Severe (24°F) | Feb 18 | Jan 12 | Dec 6 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | May 6 | May 1 | Apr 27 | Apr 22 | Apr 17 | Apr 12 | Apr 8 | Apr 3 | Mar 29 |
| 32°F | Apr 10 | Apr 2 | Mar 28 | Mar 23 | Mar 18 | Mar 13 | Mar 8 | Mar 1 | Feb 22 |
| 28°F | Mar 10 | Feb 28 | Feb 23 | Feb 18 | Feb 13 | Feb 7 | Jan 28 | Jan 13 | Dec 30 |
| 24°F | Feb 18 | Feb 11 | Feb 1 | Jan 22 | Jan 12 | Jan 3 | Dec 25 | Dec 15 | Dec 6 |
| 20°F | Feb 14 | Feb 2 | Jan 23 | Jan 8 | Jan 1 | Dec 24 | Dec 17 | Dec 12 | Dec 2 |
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 11 | Oct 27 | Nov 15 |
| Freeze (32°F) | Oct 27 | Nov 13 | Dec 6 |
| Hard (28°F) | Nov 9 | Dec 1 | Dec 31 |
| Severe (24°F) | Nov 20 | Dec 18 | Feb 2 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Oct 11 | Oct 17 | Oct 20 | Oct 24 | Oct 27 | Oct 30 | Nov 1 | Nov 7 | Nov 15 |
| 32°F | Oct 27 | Nov 1 | Nov 5 | Nov 10 | Nov 13 | Nov 18 | Nov 23 | Nov 30 | Dec 6 |
| 28°F | Nov 9 | Nov 14 | Nov 21 | Nov 26 | Dec 1 | Dec 6 | Dec 13 | Dec 20 | Dec 31 |
| 24°F | Nov 20 | Nov 29 | Dec 6 | Dec 12 | Dec 18 | Dec 27 | Jan 2 | Jan 15 | Feb 2 |
| 20°F | Nov 30 | Dec 7 | Dec 12 | Dec 19 | Dec 28 | Jan 1 | Jan 11 | Jan 25 | 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: N Willamette Exp Stn, Or, about 2.1 miles away@if(!empty($station['elevation_ft'])), at 150 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 Wilsonville, OR?
On average, the last spring frost (32°F) around Wilsonville, OR is about Mar 18. In cooler years it can run later, so for a safer bet many gardeners wait until Feb 22.
When is the first frost in the fall?
The first fall frost around Wilsonville, OR typically arrives about Nov 13. 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 18 on average, or Feb 22 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 243 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 97070 Planting calendar → Oregon frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026