Last spring frost
May 8
Frost Dates for Vernonia, OR
First fall frost
Oct 1
Growing season
144 days
Hardiness zone
8b
In an average year around Vernonia, OR, the last spring frost (32°F) is about May 8 and the first fall frost is about Oct 1, giving roughly a 144-day growing season. To be safe most years, wait until Apr 18 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%) |
|---|---|---|---|
| Freeze (32°F) | May 29 | May 8 | Apr 18 |
| Hard (28°F) | May 7 | Apr 12 | Mar 14 |
| Severe (24°F) | Apr 5 | Mar 5 | Feb 2 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 32°F | May 29 | May 23 | May 17 | May 12 | May 8 | May 2 | Apr 30 | Apr 26 | Apr 18 |
| 28°F | May 7 | May 1 | Apr 26 | Apr 19 | Apr 12 | Apr 7 | Apr 1 | Mar 25 | Mar 14 |
| 24°F | Apr 5 | Mar 26 | Mar 18 | Mar 12 | Mar 5 | Feb 28 | Feb 23 | Feb 18 | Feb 2 |
| 20°F | Mar 6 | Feb 28 | Feb 23 | Feb 18 | Feb 12 | Feb 1 | Jan 17 | Jan 6 | Dec 18 |
| 16°F | Feb 25 | Feb 18 | Feb 9 | Jan 29 | Jan 14 | Jan 2 | Dec 26 | Dec 12 | Dec 3 |
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%) |
|---|---|---|---|
| Freeze (32°F) | Sep 11 | Oct 1 | Oct 28 |
| Hard (28°F) | Sep 28 | Oct 21 | Nov 19 |
| Severe (24°F) | Oct 14 | Nov 15 | Dec 20 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 32°F | Sep 11 | Sep 18 | Sep 24 | Sep 28 | Oct 1 | Oct 6 | Oct 10 | Oct 18 | Oct 28 |
| 28°F | Sep 28 | Oct 3 | Oct 8 | Oct 15 | Oct 21 | Oct 26 | Nov 1 | Nov 9 | Nov 19 |
| 24°F | Oct 14 | Oct 25 | Nov 1 | Nov 9 | Nov 15 | Nov 23 | Nov 28 | Dec 6 | Dec 20 |
| 20°F | Nov 4 | Nov 14 | Nov 23 | Nov 29 | Dec 5 | Dec 14 | Dec 24 | Jan 1 | Jan 20 |
| 16°F | Nov 13 | Nov 27 | Dec 3 | Dec 9 | Dec 17 | Dec 27 | Jan 2 | Jan 22 | Feb 14 |
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: Vernonia #2, Or, about 10 miles away@if(!empty($station['elevation_ft'])), at 625 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 Vernonia, OR?
On average, the last spring frost (32°F) around Vernonia, OR is about May 8. In cooler years it can run later, so for a safer bet many gardeners wait until Apr 18.
When is the first frost in the fall?
The first fall frost around Vernonia, OR typically arrives about Oct 1. 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 May 8 on average, or Apr 18 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 144 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 97144 Planting calendar → Oregon frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026