Frost dates for Boise 7 N, ID
At Boise 7 N, the median last spring frost (32°F) is May 17 and the median first fall frost is Oct 12, for a typical growing season of 147 days. For a 90% chance that the last frost has passed, wait until Jun 10. Nearby ZIP codes are in USDA hardiness zone 7a.
- May 17Last spring frost (median)50% chance of 32°F after this date
- Jun 10Safer planting date10% chance of 32°F after this date
- Oct 12First fall frost (median)50% chance of 32°F by this date
- 147 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 | May 18 | Jun 6 | Jun 23 |
| 32°F | Apr 27 | May 17 | Jun 10 |
| 28°F | Apr 7 | Apr 27 | May 19 |
| 24°F | Mar 7 | Apr 4 | Apr 29 |
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 13 | Sep 29 | Oct 16 |
| 32°F | Sep 27 | Oct 12 | Oct 30 |
| 28°F | Oct 8 | Oct 24 | Nov 11 |
| 24°F | Oct 19 | Nov 5 | Nov 24 |
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 | 88 days | 114 days | 140 days |
| 32°F | 120 days | 147 days | 172 days |
| 28°F | 152 days | 179 days | 203 days |
| 24°F | 182 days | 212 days | 244 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 |
|---|---|---|---|
| 83714 | 7a | 0 to 5°F | 7 km |
| 83703 | 7a | 0 to 5°F | 9 km |
| 83702 | 7a | 0 to 5°F | 9 km |
| 83629 | 7a | 0 to 5°F | 20 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 USC00101017, at 43.7383, -116.2022, elevation 1184 m (3,885 ft).
- Data quality: Standard (24+ years of data), 29 years of freeze data.
- Average days per year at or below 32°F: 125.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Boise Air Terminal (19 km)
- Emmett 2 E (25 km)
- Boise Lucky Peak Dam (27 km)
- Arrowrock Dam (28 km)
- Idaho City (32 km)
- Nampa Sugar Factory (34 km)
- Garden Valley (44 km)
- Deer Flat Dam (47 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.