Frost dates for Dworshak Fish Hatchery, ID
At Dworshak Fish Hatchery, the median last spring frost (32°F) is Apr 20 and the median first fall frost is Oct 20, for a typical growing season of 182 days. For a 90% chance that the last frost has passed, wait until May 5. Nearby ZIP codes are in USDA hardiness zone 7a.
- Apr 20Last spring frost (median)50% chance of 32°F after this date
- May 5Safer planting date10% chance of 32°F after this date
- Oct 20First fall frost (median)50% chance of 32°F by this date
- 182 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 5 | May 19 |
| 32°F | Apr 1 | Apr 20 | May 5 |
| 28°F | Mar 7 | Mar 28 | Apr 18 |
| 24°F | Feb 10 | Mar 4 | Mar 26 |
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 20 | Oct 6 | Oct 24 |
| 32°F | Sep 30 | Oct 20 | Nov 7 |
| 28°F | Oct 14 | Nov 2 | Nov 23 |
| 24°F | Oct 25 | Nov 19 | Dec 11 |
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 | 131 days | 153 days | 173 days |
| 32°F | 158 days | 182 days | 207 days |
| 28°F | 190 days | 219 days | 249 days |
| 24°F | 227 days | 261 days | 295 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 |
|---|---|---|---|
| 83520 | 7a | 0 to 5°F | 5 km |
| 83545 | 7a | 0 to 5°F | 11 km |
| 83544 | 7a | 0 to 5°F | 13 km |
| 83541 | 7a | 0 to 5°F | 14 km |
| 83537 | 7a | 0 to 5°F | 22 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 USC00102845, at 46.5022, -116.3217, elevation 303 m (995 ft).
- Data quality: Standard (24+ years of data), 29 years of freeze data.
- Average days per year at or below 32°F: 101.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Nezperce (31 km)
- Elk River (33 km)
- Winchester (37 km)
- Kamiah (37 km)
- Pierce (40 km)
- Headquarters (42 km)
- Cottonwood 2 WSW (52 km)
- Moscow U Of I (55 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.