Last spring frost
May 19
Frost Dates for Prospect, OR
First fall frost
Oct 3
Growing season
136 days
Hardiness zone
8a
In an average year around Prospect, OR, the last spring frost (32°F) is about May 19 and the first fall frost is about Oct 3, giving roughly a 136-day growing season. To be safe most years, wait until Apr 29 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 28 | Jun 11 | May 22 |
| Freeze (32°F) | Jun 9 | May 19 | Apr 29 |
| Hard (28°F) | May 16 | Apr 26 | Apr 1 |
| Severe (24°F) | Apr 21 | Mar 17 | Feb 14 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Jun 28 | Jun 22 | Jun 18 | Jun 14 | Jun 11 | Jun 7 | Jun 2 | May 30 | May 22 |
| 32°F | Jun 9 | Jun 1 | May 28 | May 23 | May 19 | May 15 | May 11 | May 6 | Apr 29 |
| 28°F | May 16 | May 8 | May 3 | Apr 30 | Apr 26 | Apr 22 | Apr 18 | Apr 11 | Apr 1 |
| 24°F | Apr 21 | Apr 10 | Mar 31 | Mar 24 | Mar 17 | Mar 10 | Mar 3 | Feb 25 | Feb 14 |
| 20°F | Mar 8 | Feb 28 | Feb 23 | Feb 15 | Feb 7 | Jan 29 | Jan 17 | Jan 6 | Dec 24 |
| 16°F | Feb 22 | Feb 12 | Jan 28 | Jan 17 | Jan 9 | Jan 3 | Dec 30 | Dec 22 | Dec 9 |
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) | Aug 29 | Sep 14 | Oct 1 |
| Freeze (32°F) | Sep 13 | Oct 3 | Oct 20 |
| Hard (28°F) | Oct 4 | Oct 24 | Nov 18 |
| Severe (24°F) | Oct 20 | Nov 17 | Dec 14 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Aug 29 | Sep 4 | Sep 7 | Sep 11 | Sep 14 | Sep 18 | Sep 21 | Sep 25 | Oct 1 |
| 32°F | Sep 13 | Sep 19 | Sep 26 | Sep 30 | Oct 3 | Oct 6 | Oct 10 | Oct 15 | Oct 20 |
| 28°F | Oct 4 | Oct 11 | Oct 16 | Oct 20 | Oct 24 | Oct 29 | Nov 2 | Nov 8 | Nov 18 |
| 24°F | Oct 20 | Oct 31 | Nov 5 | Nov 11 | Nov 17 | Nov 24 | Dec 1 | Dec 5 | Dec 14 |
| 20°F | Nov 12 | Nov 21 | Nov 28 | Dec 2 | Dec 7 | Dec 14 | Dec 21 | Dec 29 | Jan 11 |
| 16°F | Nov 29 | Dec 4 | Dec 10 | Dec 17 | Dec 23 | Dec 29 | Jan 3 | Jan 14 | Jan 28 |
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: Prospect 2 Sw, Or, about 8.1 miles away@if(!empty($station['elevation_ft'])), at 2,482 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 Prospect, OR?
On average, the last spring frost (32°F) around Prospect, OR is about May 19. In cooler years it can run later, so for a safer bet many gardeners wait until Apr 29.
When is the first frost in the fall?
The first fall frost around Prospect, 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 19 on average, or Apr 29 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 136 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 97522 Planting calendar → Oregon frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026