Frost dates for Hill City 1 W, ID
At Hill City 1 W, the median last spring frost (32°F) is Jun 16 and the median first fall frost is Sep 6, for a typical growing season of 80 days. For a 90% chance that the last frost has passed, wait until Jul 3. Nearby ZIP codes are in USDA hardiness zone 5a.
- Jun 16Last spring frost (median)50% chance of 32°F after this date
- Jul 3Safer planting date10% chance of 32°F after this date
- Sep 6First fall frost (median)50% chance of 32°F by this date
- 80 daysGrowing season (median)between 32°F freezes
USDA hardiness zone 5a (-20 to -15°F) · see all zone 5a frost dates
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 |
|---|---|---|---|
| 32°F | May 31 | Jun 16 | Jul 3 |
| 28°F | May 6 | May 30 | Jun 21 |
| 24°F | Apr 15 | May 3 | May 30 |
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 |
|---|---|---|---|
| 32°F | Aug 20 | Sep 6 | Sep 22 |
| 28°F | Sep 2 | Sep 18 | Oct 5 |
| 24°F | Sep 10 | Sep 29 | Oct 15 |
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 | 32 days | 54 days | 76 days |
| 32°F | 57 days | 80 days | 103 days |
| 28°F | 82 days | 109 days | 136 days |
| 24°F | 116 days | 145 days | 170 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 |
|---|---|---|---|
| 83322 | 5a | -20 to -15°F | 9 km |
| 83337 | 5a | -20 to -15°F | 11 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 USC00104268, at 43.2994, -115.0733, elevation 1554 m (5,100 ft).
- Data quality: Representative (10+ years), 15 years of freeze data.
- Average days per year at or below 32°F: 212.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Fairfield Ranger Station (23 km)
- Glenns Ferry (45 km)
- Mountain Home (55 km)
- Hagerman 2 SW (56 km)
- Shoshone 1 WNW (67 km)
- Bellevue (68 km)
- Ketchum Ranger Station (72 km)
- Bruneau (75 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.