Last spring frost
May 7
Frost Dates for Unity, OR
First fall frost
Oct 3
Growing season
147 days
Hardiness zone
6a
In an average year around Unity, OR, the last spring frost (32°F) is about May 7 and the first fall frost is about Oct 3, giving roughly a 147-day growing season. To be safe most years, wait until Apr 23 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) | Jun 15 | May 22 | May 7 |
| Freeze (32°F) | May 28 | May 7 | Apr 23 |
| Hard (28°F) | May 11 | Apr 24 | Apr 4 |
| Severe (24°F) | Apr 29 | Apr 7 | Mar 13 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Jun 15 | Jun 7 | Jun 2 | May 27 | May 22 | May 17 | May 14 | May 11 | May 7 |
| 32°F | May 28 | May 17 | May 13 | May 10 | May 7 | May 4 | May 1 | Apr 29 | Apr 23 |
| 28°F | May 11 | May 5 | Apr 30 | Apr 27 | Apr 24 | Apr 21 | Apr 17 | Apr 11 | Apr 4 |
| 24°F | Apr 29 | Apr 21 | Apr 17 | Apr 11 | Apr 7 | Apr 2 | Mar 28 | Mar 21 | Mar 13 |
| 20°F | Apr 13 | Apr 4 | Mar 29 | Mar 19 | Mar 12 | Mar 8 | Mar 3 | Feb 27 | Feb 20 |
| 16°F | Mar 13 | Mar 6 | Mar 1 | Feb 27 | Feb 23 | Feb 19 | Feb 16 | Feb 10 | Jan 31 |
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) | Sep 6 | Sep 22 | Oct 5 |
| Freeze (32°F) | Sep 19 | Oct 3 | Oct 14 |
| Hard (28°F) | Sep 29 | Oct 13 | Oct 25 |
| Severe (24°F) | Oct 9 | Oct 25 | Nov 8 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 6 | Sep 12 | Sep 16 | Sep 19 | Sep 22 | Sep 24 | Sep 27 | Oct 1 | Oct 5 |
| 32°F | Sep 19 | Sep 24 | Sep 28 | Sep 30 | Oct 3 | Oct 5 | Oct 8 | Oct 10 | Oct 14 |
| 28°F | Sep 29 | Oct 4 | Oct 7 | Oct 10 | Oct 13 | Oct 16 | Oct 19 | Oct 22 | Oct 25 |
| 24°F | Oct 9 | Oct 15 | Oct 19 | Oct 23 | Oct 25 | Oct 28 | Oct 31 | Nov 2 | Nov 8 |
| 20°F | Oct 21 | Oct 26 | Oct 31 | Nov 2 | Nov 5 | Nov 9 | Nov 13 | Nov 18 | Nov 23 |
| 16°F | Oct 31 | Nov 5 | Nov 10 | Nov 14 | Nov 18 | Nov 22 | Nov 25 | Nov 30 | Dec 7 |
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: Westfall, Or, about 20.2 miles away@if(!empty($station['elevation_ft'])), at 3,040 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 Unity, OR?
On average, the last spring frost (32°F) around Unity, OR is about May 7. In cooler years it can run later, so for a safer bet many gardeners wait until Apr 23.
When is the first frost in the fall?
The first fall frost around Unity, OR typically arrives about Oct 3. 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 7 on average, or Apr 23 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 147 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 97908 Planting calendar → Oregon frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026