Frost dates for Winchester, ID
At Winchester, the median last spring frost (32°F) is May 23 and the median first fall frost is Sep 25, for a typical growing season of 121 days. For a 90% chance that the last frost has passed, wait until Jun 19. Nearby ZIP codes are in USDA hardiness zones 6b to 7b.
- May 23Last spring frost (median)50% chance of 32°F after this date
- Jun 19Safer planting date10% chance of 32°F after this date
- Sep 25First fall frost (median)50% chance of 32°F by this date
- 121 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 | Jun 1 | Jun 18 | Jul 12 |
| 32°F | May 4 | May 23 | Jun 19 |
| 28°F | Apr 13 | May 2 | May 24 |
| 24°F | Mar 21 | Apr 10 | May 1 |
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 | Aug 21 | Sep 8 | Sep 26 |
| 32°F | Sep 7 | Sep 25 | Oct 10 |
| 28°F | Sep 21 | Oct 9 | Oct 28 |
| 24°F | Oct 5 | Oct 26 | Nov 13 |
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 | 53 days | 80 days | 104 days |
| 32°F | 89 days | 121 days | 147 days |
| 28°F | 129 days | 160 days | 185 days |
| 24°F | 167 days | 196 days | 222 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 |
|---|---|---|---|
| 83523 | 6b | -5 to 0°F | 12 km |
| 83524 | 7a | 0 to 5°F | 13 km |
| 83548 | 6b | -5 to 0°F | 14 km |
| 83540 | 7b | 5 to 10°F | 17 km |
| 83555 | 6b | -5 to 0°F | 19 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 USC00109846, at 46.2381, -116.6233, elevation 1211 m (3,972 ft).
- Data quality: Representative (10+ years), 23 years of freeze data.
- Average days per year at or below 32°F: 170.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Cottonwood 2 WSW (29 km)
- Nezperce (29 km)
- Lewiston Nez Perce Co Airport (34 km)
- Dworshak Fish Hatchery (37 km)
- Kamiah (45 km)
- Grangeville (51 km)
- Kooskia 5 SSE (56 km)
- Moscow U Of I (60 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.