Last spring frost
Apr 11
Frost Dates for Harrisburg, OR
First fall frost
Oct 23
Growing season
196 days
Hardiness zone
8b
In an average year around Harrisburg, OR, the last spring frost (32°F) is about Apr 11 and the first fall frost is about Oct 23, giving roughly a 196-day growing season. To be safe most years, wait until Mar 15 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 8 | May 15 | Apr 24 |
| Freeze (32°F) | May 9 | Apr 11 | Mar 15 |
| Hard (28°F) | Mar 30 | Mar 3 | Feb 2 |
| Severe (24°F) | Feb 27 | Feb 1 | Dec 21 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Jun 8 | Jun 1 | May 25 | May 19 | May 15 | May 11 | May 5 | Apr 30 | Apr 24 |
| 32°F | May 9 | Apr 30 | Apr 25 | Apr 17 | Apr 11 | Apr 3 | Mar 29 | Mar 23 | Mar 15 |
| 28°F | Mar 30 | Mar 22 | Mar 14 | Mar 8 | Mar 3 | Feb 27 | Feb 23 | Feb 16 | Feb 2 |
| 24°F | Feb 27 | Feb 22 | Feb 17 | Feb 12 | Feb 1 | Jan 24 | Jan 12 | Jan 3 | Dec 21 |
| 20°F | Feb 17 | Feb 1 | Jan 21 | Jan 13 | Jan 5 | Dec 31 | Dec 21 | Dec 12 | Dec 2 |
| 16°F | Jan 13 | Jan 4 | Dec 31 | Dec 23 | Dec 17 | Dec 13 | Dec 10 | Dec 5 | Nov 29 |
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 18 | Oct 7 | Oct 24 |
| Freeze (32°F) | Oct 6 | Oct 23 | Nov 13 |
| Hard (28°F) | Oct 20 | Nov 11 | Dec 12 |
| Severe (24°F) | Nov 2 | Dec 5 | Jan 12 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 18 | Sep 26 | Oct 1 | Oct 4 | Oct 7 | Oct 10 | Oct 13 | Oct 18 | Oct 24 |
| 32°F | Oct 6 | Oct 11 | Oct 15 | Oct 19 | Oct 23 | Oct 27 | Oct 31 | Nov 5 | Nov 13 |
| 28°F | Oct 20 | Oct 28 | Nov 1 | Nov 6 | Nov 11 | Nov 17 | Nov 24 | Dec 2 | Dec 12 |
| 24°F | Nov 2 | Nov 12 | Nov 21 | Nov 29 | Dec 5 | Dec 13 | Dec 22 | Dec 30 | Jan 12 |
| 20°F | Nov 10 | Nov 26 | Dec 2 | Dec 10 | Dec 19 | Dec 28 | Jan 2 | Jan 14 | Jan 30 |
| 16°F | Nov 17 | Dec 1 | Dec 5 | Dec 9 | Dec 13 | Dec 18 | Dec 26 | Jan 1 | Jan 11 |
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: Eugene Mahlon Sweet Ap, Or, about 12.3 miles away@if(!empty($station['elevation_ft'])), at 353 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 Harrisburg, OR?
On average, the last spring frost (32°F) around Harrisburg, OR is about Apr 11. In cooler years it can run later, so for a safer bet many gardeners wait until Mar 15.
When is the first frost in the fall?
The first fall frost around Harrisburg, OR typically arrives about Oct 23. 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 Apr 11 on average, or Mar 15 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 196 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 97446 Planting calendar → Oregon frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026