Frost dates for Boise Air Terminal, ID
At Boise Air Terminal, the median last spring frost (32°F) is Apr 24 and the median first fall frost is Oct 21, for a typical growing season of 179 days. For a 90% chance that the last frost has passed, wait until May 9. Nearby ZIP codes are in USDA hardiness zone 7a.
- Apr 24Last spring frost (median)50% chance of 32°F after this date
- May 9Safer planting date10% chance of 32°F after this date
- Oct 21First fall frost (median)50% chance of 32°F by this date
- 179 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 23 | May 8 | May 29 |
| 32°F | Apr 4 | Apr 24 | May 9 |
| 28°F | Mar 10 | Apr 2 | Apr 25 |
| 24°F | Feb 16 | Mar 9 | Apr 4 |
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 25 | Oct 8 | Oct 25 |
| 32°F | Oct 5 | Oct 21 | Nov 5 |
| 28°F | Oct 17 | Oct 31 | Nov 19 |
| 24°F | Oct 24 | Nov 13 | Dec 1 |
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 | 128 days | 153 days | 173 days |
| 32°F | 156 days | 179 days | 203 days |
| 28°F | 186 days | 212 days | 241 days |
| 24°F | 215 days | 246 days | 276 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 |
|---|---|---|---|
| 83705 | 7a | 0 to 5°F | 2 km |
| 83709 | 7a | 0 to 5°F | 4 km |
| 83706 | 7a | 0 to 5°F | 5 km |
| 83720 | 7a | 0 to 5°F | 7 km |
| 83704 | 7a | 0 to 5°F | 8 km |
| 83713 | 7a | 0 to 5°F | 11 km |
| 83642 | 7a | 0 to 5°F | 13 km |
| 83634 | 7a | 0 to 5°F | 15 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 USW00024131, at 43.5667, -116.2406, elevation 858 m (2,814 ft).
- Data quality: Standard (24+ years of data), 27 years of freeze data.
- Average days per year at or below 32°F: 108.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Boise Lucky Peak Dam (16 km)
- Boise 7 N (19 km)
- Arrowrock Dam (26 km)
- Nampa Sugar Factory (27 km)
- Emmett 2 E (37 km)
- Swan Falls Ph (38 km)
- Deer Flat Dam (41 km)
- Idaho City (45 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.