Frost dates for Nampa Sugar Factory, ID
At Nampa Sugar Factory, the median last spring frost (32°F) is Apr 29 and the median first fall frost is Oct 13, for a typical growing season of 164 days. For a 90% chance that the last frost has passed, wait until May 18. Nearby ZIP codes are in USDA hardiness zone 7a.
- Apr 29Last spring frost (median)50% chance of 32°F after this date
- May 18Safer planting date10% chance of 32°F after this date
- Oct 13First fall frost (median)50% chance of 32°F by this date
- 164 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 1 | May 16 | Jun 6 |
| 32°F | Apr 15 | Apr 29 | May 18 |
| 28°F | Mar 25 | Apr 11 | May 1 |
| 24°F | Mar 2 | Mar 22 | Apr 12 |
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 15 | Sep 30 | Oct 14 |
| 32°F | Sep 29 | Oct 13 | Oct 28 |
| 28°F | Oct 9 | Oct 25 | Nov 10 |
| 24°F | Oct 22 | Nov 6 | 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 | 111 days | 134 days | 155 days |
| 32°F | 142 days | 164 days | 186 days |
| 28°F | 169 days | 195 days | 220 days |
| 24°F | 201 days | 227 days | 254 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 |
|---|---|---|---|
| 83687 | 7a | 0 to 5°F | 4 km |
| 83651 | 7a | 0 to 5°F | 5 km |
| 83605 | 7a | 0 to 5°F | 9 km |
| 83686 | 7a | 0 to 5°F | 12 km |
| 83646 | 7a | 0 to 5°F | 13 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 USC00106305, at 43.6039, -116.5753, elevation 753 m (2,470 ft).
- Data quality: Representative (10+ years), 22 years of freeze data.
- Average days per year at or below 32°F: 132.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Deer Flat Dam (14 km)
- Boise Air Terminal (27 km)
- Homedale 1 SE (28 km)
- Emmett 2 E (29 km)
- Boise 7 N (34 km)
- Parma Exp. Station (37 km)
- Boise Lucky Peak Dam (43 km)
- Swan Falls Ph (43 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.