Last spring frost
Jun 3
Frost Dates for Fossil, OR
First fall frost
Sep 14
Growing season
98 days
Hardiness zone
7a
In an average year around Fossil, OR, the last spring frost (32°F) is about Jun 3 and the first fall frost is about Sep 14, giving roughly a 98-day growing season. To be safe most years, wait until May 13 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) | Jul 3 | Jun 3 | May 13 |
| Hard (28°F) | Jun 1 | May 10 | Apr 24 |
| Severe (24°F) | May 10 | Apr 24 | Mar 31 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 32°F | Jul 3 | Jun 24 | Jun 17 | Jun 10 | Jun 3 | May 30 | May 26 | May 20 | May 13 |
| 28°F | Jun 1 | May 23 | May 17 | May 13 | May 10 | May 6 | May 2 | Apr 29 | Apr 24 |
| 24°F | May 10 | May 4 | Apr 30 | Apr 27 | Apr 24 | Apr 20 | Apr 16 | Apr 11 | Mar 31 |
| 20°F | Apr 23 | Apr 16 | Apr 11 | Apr 6 | Apr 1 | Mar 28 | Mar 21 | Mar 13 | Mar 2 |
| 16°F | Apr 4 | Mar 26 | Mar 15 | Mar 8 | Mar 2 | Feb 26 | Feb 19 | Feb 12 | Jan 24 |
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) | Aug 25 | Sep 14 | Oct 3 |
| Hard (28°F) | Sep 10 | Oct 2 | Oct 23 |
| Severe (24°F) | Sep 29 | Oct 17 | Nov 8 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 32°F | Aug 25 | Sep 1 | Sep 5 | Sep 9 | Sep 14 | Sep 18 | Sep 23 | Sep 29 | Oct 3 |
| 28°F | Sep 10 | Sep 21 | Sep 25 | Sep 30 | Oct 2 | Oct 5 | Oct 9 | Oct 14 | Oct 23 |
| 24°F | Sep 29 | Oct 3 | Oct 8 | Oct 13 | Oct 17 | Oct 23 | Oct 27 | Nov 1 | Nov 8 |
| 20°F | Oct 9 | Oct 17 | Oct 23 | Oct 28 | Nov 1 | Nov 7 | Nov 13 | Nov 21 | Dec 1 |
| 16°F | Oct 19 | Oct 30 | Nov 6 | Nov 13 | Nov 21 | Nov 27 | Dec 3 | Dec 10 | Dec 19 |
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: Fossil, Or, about 2.8 miles away@if(!empty($station['elevation_ft'])), at 2,650 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 Fossil, OR?
On average, the last spring frost (32°F) around Fossil, OR is about Jun 3. In cooler years it can run later, so for a safer bet many gardeners wait until May 13.
When is the first frost in the fall?
The first fall frost around Fossil, OR typically arrives about Sep 14. 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 Jun 3 on average, or May 13 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 98 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 97830 Planting calendar → Oregon frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026