Frost dates for Malheur Branch Exp. Station, OR
At Malheur Branch Exp. Station, the median last spring frost (32°F) is Apr 23 and the median first fall frost is Oct 13, for a typical growing season of 173 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 23Last spring frost (median)50% chance of 32°F after this date
- May 9Safer planting date10% chance of 32°F after this date
- Oct 13First fall frost (median)50% chance of 32°F by this date
- 173 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 22 | May 6 | May 24 |
| 32°F | Apr 6 | Apr 23 | May 9 |
| 28°F | Mar 15 | Apr 6 | Apr 25 |
| 24°F | Feb 21 | Mar 12 | Apr 7 |
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 2 | Oct 16 |
| 32°F | Oct 1 | Oct 13 | Oct 29 |
| 28°F | Oct 12 | Oct 26 | Nov 10 |
| 24°F | Oct 24 | Nov 8 | Nov 23 |
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 | 123 days | 147 days | 167 days |
| 32°F | 151 days | 173 days | 195 days |
| 28°F | 178 days | 204 days | 228 days |
| 24°F | 209 days | 237 days | 265 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 |
|---|---|---|---|
| 83619 | 7a | 0 to 5°F | 9 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 USC00355160, at 43.9794, -117.0247, elevation 689 m (2,260 ft).
- Data quality: Representative (10+ years), 25 years of freeze data.
- Average days per year at or below 32°F: 135.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Ontario Muni Airport (5 km)
- Ontario Ksrv (8 km)
- Nyssa (12 km)
- Vale (18 km)
- Owyhee Dam (41 km)
- Huntington (46 km)
- Westfall (56 km)
- Rockville 5 N (69 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.