Last spring frost
May 17
Frost Dates for Horseshoe Bend, ID
First fall frost
Oct 12
Growing season
147 days
Hardiness zone
7a
In an average year around Horseshoe Bend, ID, the last spring frost (32°F) is about May 17 and the first fall frost is about Oct 12, giving roughly a 147-day growing season. To be safe most years, wait until Apr 27 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 23 | Jun 6 | May 18 |
| Freeze (32°F) | Jun 10 | May 17 | Apr 27 |
| Hard (28°F) | May 19 | Apr 27 | Apr 7 |
| Severe (24°F) | Apr 29 | Apr 4 | Mar 7 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Jun 23 | Jun 16 | Jun 13 | Jun 9 | Jun 6 | Jun 3 | May 31 | May 25 | May 18 |
| 32°F | Jun 10 | Jun 3 | May 28 | May 22 | May 17 | May 13 | May 8 | May 3 | Apr 27 |
| 28°F | May 19 | May 11 | May 5 | May 1 | Apr 27 | Apr 24 | Apr 20 | Apr 15 | Apr 7 |
| 24°F | Apr 29 | Apr 20 | Apr 13 | Apr 9 | Apr 4 | Mar 30 | Mar 25 | Mar 16 | Mar 7 |
| 20°F | Apr 2 | Mar 24 | Mar 14 | Mar 9 | Mar 4 | Feb 28 | Feb 24 | Feb 18 | Feb 13 |
| 16°F | Mar 7 | Mar 1 | Feb 25 | Feb 20 | Feb 17 | Feb 12 | Feb 6 | Jan 31 | Jan 20 |
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 13 | Sep 29 | Oct 16 |
| Freeze (32°F) | Sep 27 | Oct 12 | Oct 30 |
| Hard (28°F) | Oct 8 | Oct 24 | Nov 11 |
| Severe (24°F) | Oct 19 | Nov 5 | Nov 24 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 13 | Sep 19 | Sep 24 | Sep 27 | Sep 29 | Oct 2 | Oct 6 | Oct 10 | Oct 16 |
| 32°F | Sep 27 | Oct 1 | Oct 5 | Oct 9 | Oct 12 | Oct 15 | Oct 19 | Oct 23 | Oct 30 |
| 28°F | Oct 8 | Oct 13 | Oct 18 | Oct 21 | Oct 24 | Oct 28 | Oct 31 | Nov 4 | Nov 11 |
| 24°F | Oct 19 | Oct 25 | Oct 30 | Nov 2 | Nov 5 | Nov 9 | Nov 13 | Nov 18 | Nov 24 |
| 20°F | Oct 29 | Nov 4 | Nov 9 | Nov 13 | Nov 18 | Nov 22 | Nov 25 | Nov 29 | Dec 4 |
| 16°F | Nov 7 | Nov 13 | Nov 20 | Nov 24 | Nov 28 | Dec 1 | Dec 4 | Dec 9 | Dec 17 |
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: Boise 7 N, Id, about 12.5 miles away@if(!empty($station['elevation_ft'])), at 3,885 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 Horseshoe Bend, ID?
On average, the last spring frost (32°F) around Horseshoe Bend, ID is about May 17. In cooler years it can run later, so for a safer bet many gardeners wait until Apr 27.
When is the first frost in the fall?
The first fall frost around Horseshoe Bend, ID typically arrives about Oct 12. 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 17 on average, or Apr 27 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 147 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 83629 Planting calendar → Idaho frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026