Frost dates for Mountain Home, ID
At Mountain Home, the median last spring frost (32°F) is May 2 and the median first fall frost is Oct 8, for a typical growing season of 157 days. For a 90% chance that the last frost has passed, wait until May 23. Nearby ZIP codes are in USDA hardiness zones 6b to 7a.
- May 2Last spring frost (median)50% chance of 32°F after this date
- May 23Safer planting date10% chance of 32°F after this date
- Oct 8First fall frost (median)50% chance of 32°F by this date
- 157 daysGrowing season (median)between 32°F freezes
Last spring frost dates
The chance that the temperature drops to the threshold after each date.
| Temperature | 90% chance later | 50% chance later | 10% chance later |
|---|---|---|---|
| 36°F | Apr 30 | May 17 | Jun 10 |
| 32°F | Apr 18 | May 2 | May 23 |
| 28°F | Apr 1 | Apr 18 | May 8 |
| 24°F | Mar 7 | Apr 2 | Apr 26 |
First fall frost dates
The chance that the temperature has dropped to the threshold by each date.
| Temperature | 10% chance by | 50% chance by | 90% chance by |
|---|---|---|---|
| 36°F | Sep 11 | Sep 28 | Oct 11 |
| 32°F | Sep 25 | Oct 8 | Oct 24 |
| 28°F | Oct 4 | Oct 20 | Nov 5 |
| 24°F | Oct 14 | Oct 31 | Nov 21 |
Growing season length
Days between the last spring and first fall freeze, as the length reached in 9, 5 and 1 out of 10 years.
| Temperature | 9 in 10 years at least | 5 in 10 years at least | 1 in 10 years at least |
|---|---|---|---|
| 36°F | 106 days | 131 days | 154 days |
| 32°F | 131 days | 157 days | 180 days |
| 28°F | 159 days | 185 days | 208 days |
| 24°F | 185 days | 213 days | 241 days |
Chance of a freeze in any year
| Temperature | Chance per year |
|---|---|
| 36°F | 100% |
| 32°F | 100% |
| 28°F | 100% |
| 24°F | 100% |
ZIP codes whose closest station is this one
| ZIP | Hardiness zone | Avg. extreme low | Distance |
|---|---|---|---|
| 83648 | 7a | 0 to 5°F | 15 km |
| 83647 | 6b | -5 to 0°F | 34 km |
Not the official USDA Plant Hardiness Zone Map. Zones shown here are the values published in the USDA-ARS / Oregon State University PRISM Group 2023 ZIP code tables, shown unaltered. For the official interactive map, visit planthardiness.ars.usda.gov.
About this station
- NOAA station ID USC00106174, at 43.1261, -115.7119, elevation 957 m (3,140 ft).
- Data quality: Representative (10+ years), 16 years of freeze data.
- Average days per year at or below 32°F: 139.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Bruneau (28 km)
- Glenns Ferry (38 km)
- Grand View 4 NW (40 km)
- Boise Lucky Peak Dam (52 km)
- Arrowrock Dam (55 km)
- Hill City 1 W (55 km)
- Swan Falls Ph (56 km)
- Boise Air Terminal (65 km)
Sources
- NOAA National Centers for Environmental Information, U.S. Climate Normals 1991–2020, annual/seasonal normals by station (version 1.0.1), file dated June 27, 2023; documentation.
- USDA Agricultural Research Service and PRISM Group, Oregon State University, 2023 Plant Hardiness Zone Map ZIP code tables (CONUS, Alaska, Hawaii, Puerto Rico), files dated November 17, 2023. Data © PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed November 1, 2026. Official map: planthardiness.ars.usda.gov.
- U.S. Census Bureau, 2024 Gazetteer ZIP Code Tabulation Areas file, dated August 30, 2024 (ZIP centroids used to find the nearest station).
Freeze dates are 30-year probabilities, not forecasts. Check your local forecast before planting tender plants.