Frost dates for Glenns Ferry, ID
At Glenns Ferry, the median last spring frost (32°F) is May 1 and the median first fall frost is Oct 3, for a typical growing season of 154 days. For a 90% chance that the last frost has passed, wait until May 16. Nearby ZIP codes are in USDA hardiness zone 7a.
- May 1Last spring frost (median)50% chance of 32°F after this date
- May 16Safer planting date10% chance of 32°F after this date
- Oct 3First fall frost (median)50% chance of 32°F by this date
- 154 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 15 | Jun 5 |
| 32°F | Apr 14 | May 1 | May 16 |
| 28°F | Mar 24 | Apr 15 | May 2 |
| 24°F | Mar 3 | Mar 25 | Apr 18 |
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 5 | Sep 21 | Oct 7 |
| 32°F | Sep 16 | Oct 3 | Oct 19 |
| 28°F | Sep 29 | Oct 16 | Nov 1 |
| 24°F | Oct 9 | Oct 29 | Nov 18 |
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 | 102 days | 128 days | 150 days |
| 32°F | 131 days | 154 days | 176 days |
| 28°F | 159 days | 184 days | 209 days |
| 24°F | 188 days | 217 days | 247 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 |
|---|---|---|---|
| 83623 | 7a | 0 to 5°F | 13 km |
| 83633 | 7a | 0 to 5°F | 15 km |
| 83627 | 7a | 0 to 5°F | 18 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 USC00103631, at 42.9403, -115.3231, elevation 752 m (2,466 ft).
- Data quality: Representative (10+ years), 23 years of freeze data.
- Average days per year at or below 32°F: 144.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Hagerman 2 SW (36 km)
- Mountain Home (38 km)
- Bruneau (40 km)
- Hill City 1 W (45 km)
- Castleford 2 N (57 km)
- Buhl #2 (60 km)
- Fairfield Ranger Station (62 km)
- Jerome (70 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.