Frost dates for Malheur Refuge HQ, OR
At Malheur Refuge HQ, the median last spring frost (32°F) is May 29 and the median first fall frost is Sep 18, for a typical growing season of 113 days. For a 90% chance that the last frost has passed, wait until Jun 17. Nearby ZIP codes are in USDA hardiness zone 6a.
- May 29Last spring frost (median)50% chance of 32°F after this date
- Jun 17Safer planting date10% chance of 32°F after this date
- Sep 18First fall frost (median)50% chance of 32°F by this date
- 113 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 |
|---|---|---|---|
| 32°F | May 6 | May 29 | Jun 17 |
| 28°F | Apr 20 | May 3 | May 24 |
| 24°F | Apr 1 | Apr 20 | May 5 |
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 |
|---|---|---|---|
| 32°F | Sep 2 | Sep 18 | Oct 3 |
| 28°F | Sep 13 | Oct 1 | Oct 18 |
| 24°F | Sep 27 | Oct 16 | Oct 31 |
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 | 56 days | 81 days | 103 days |
| 32°F | 85 days | 113 days | 139 days |
| 28°F | 124 days | 149 days | 171 days |
| 24°F | 153 days | 178 days | 202 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 |
|---|---|---|---|
| 97722 | 6a | -10 to -5°F | 30 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 USC00355162, at 43.2650, -118.8447, elevation 1255 m (4,118 ft).
- Data quality: Representative (10+ years), 13 years of freeze data.
- Average days per year at or below 32°F: 184.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Burns Muni Airport (38 km)
- O O Rch (38 km)
- Riverside 7 SSW (54 km)
- Drewsey (71 km)
- Riley 10 WSW (72 km)
- Squaw Butte-Northern Great Bas (75 km)
- Seneca (98 km)
- Alkali Lake (99 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.