Last spring frost
Jun 15
Frost Dates for Tetonia, ID
First fall frost
Sep 7
Growing season
85 days
Hardiness zone
5a
In an average year around Tetonia, ID, the last spring frost (32°F) is about Jun 15 and the first fall frost is about Sep 7, giving roughly a 85-day growing season. To be safe most years, wait until May 24 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 29 | Jun 15 | May 24 |
| Hard (28°F) | Jun 14 | May 21 | May 5 |
| Severe (24°F) | May 22 | May 6 | Apr 21 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 32°F | Jun 29 | Jun 24 | Jun 21 | Jun 18 | Jun 15 | Jun 11 | Jun 6 | May 31 | May 24 |
| 28°F | Jun 14 | Jun 6 | May 31 | May 25 | May 21 | May 17 | May 14 | May 10 | May 5 |
| 24°F | May 22 | May 16 | May 12 | May 9 | May 6 | May 3 | May 1 | Apr 28 | Apr 21 |
| 20°F | May 8 | May 2 | Apr 29 | Apr 26 | Apr 22 | Apr 18 | Apr 15 | Apr 11 | Apr 6 |
| 16°F | Apr 25 | Apr 18 | Apr 14 | Apr 11 | Apr 7 | Apr 5 | Apr 2 | Mar 30 | Mar 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 24 | Sep 7 | Sep 23 |
| Hard (28°F) | Sep 3 | Sep 20 | Oct 5 |
| Severe (24°F) | Sep 16 | Oct 2 | Oct 17 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 32°F | Aug 24 | Aug 30 | Sep 1 | Sep 4 | Sep 7 | Sep 11 | Sep 14 | Sep 18 | Sep 23 |
| 28°F | Sep 3 | Sep 9 | Sep 14 | Sep 17 | Sep 20 | Sep 23 | Sep 26 | Oct 1 | Oct 5 |
| 24°F | Sep 16 | Sep 22 | Sep 26 | Sep 30 | Oct 2 | Oct 5 | Oct 8 | Oct 12 | Oct 17 |
| 20°F | Sep 28 | Oct 3 | Oct 6 | Oct 10 | Oct 13 | Oct 16 | Oct 20 | Oct 24 | Oct 30 |
| 16°F | Oct 8 | Oct 14 | Oct 18 | Oct 21 | Oct 25 | Oct 29 | Nov 1 | Nov 6 | Nov 12 |
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: Tetonia Exp Stn, Id, about 6.5 miles away@if(!empty($station['elevation_ft'])), at 6,170 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 Tetonia, ID?
On average, the last spring frost (32°F) around Tetonia, ID is about Jun 15. In cooler years it can run later, so for a safer bet many gardeners wait until May 24.
When is the first frost in the fall?
The first fall frost around Tetonia, ID typically arrives about Sep 7. 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 15 on average, or May 24 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 85 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 83452 Planting calendar → Idaho frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026