Last spring frost
May 20
Frost Dates for Priest River, ID
First fall frost
Sep 13
Growing season
114 days
Hardiness zone
6a
In an average year around Priest River, ID, the last spring frost (32°F) is about May 20 and the first fall frost is about Sep 13, giving roughly a 114-day growing season. To be safe most years, wait until May 6 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) | Jun 4 | May 20 | May 6 |
| Hard (28°F) | May 17 | May 4 | Apr 19 |
| Severe (24°F) | May 3 | Apr 13 | Mar 26 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 32°F | Jun 4 | May 30 | May 27 | May 24 | May 20 | May 17 | May 14 | May 11 | May 6 |
| 28°F | May 17 | May 13 | May 10 | May 7 | May 4 | Apr 30 | Apr 29 | Apr 25 | Apr 19 |
| 24°F | May 3 | Apr 27 | Apr 23 | Apr 18 | Apr 13 | Apr 9 | Apr 4 | Mar 31 | Mar 26 |
| 20°F | Apr 13 | Apr 4 | Mar 31 | Mar 27 | Mar 22 | Mar 18 | Mar 14 | Mar 10 | Mar 5 |
| 16°F | Mar 23 | Mar 18 | Mar 14 | Mar 10 | Mar 8 | Mar 5 | Mar 2 | Feb 28 | Feb 21 |
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 1 | Sep 13 | Sep 30 |
| Hard (28°F) | Sep 12 | Sep 28 | Oct 13 |
| Severe (24°F) | Sep 26 | Oct 10 | Nov 1 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 32°F | Sep 1 | Sep 3 | Sep 7 | Sep 9 | Sep 13 | Sep 16 | Sep 19 | Sep 23 | Sep 30 |
| 28°F | Sep 12 | Sep 17 | Sep 21 | Sep 25 | Sep 28 | Oct 1 | Oct 3 | Oct 7 | Oct 13 |
| 24°F | Sep 26 | Oct 1 | Oct 4 | Oct 7 | Oct 10 | Oct 15 | Oct 19 | Oct 25 | Nov 1 |
| 20°F | Oct 6 | Oct 13 | Oct 20 | Oct 25 | Oct 29 | Nov 2 | Nov 7 | Nov 14 | Nov 21 |
| 16°F | Oct 21 | Oct 29 | Nov 4 | Nov 9 | Nov 14 | Nov 18 | Nov 24 | Nov 30 | Dec 8 |
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: Priest Rvr Exp Stn, Id, about 3.2 miles away@if(!empty($station['elevation_ft'])), at 2,371 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 Priest River, ID?
On average, the last spring frost (32°F) around Priest River, ID is about May 20. In cooler years it can run later, so for a safer bet many gardeners wait until May 6.
When is the first frost in the fall?
The first fall frost around Priest River, ID typically arrives about Sep 13. 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 20 on average, or May 6 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 114 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 83856 Planting calendar → Idaho frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026