Frost dates for Ontario Ksrv, OR
At Ontario Ksrv, the median last spring frost (32°F) is Apr 22 and the median first fall frost is Oct 9, for a typical growing season of 168 days. For a 90% chance that the last frost has passed, wait until May 7. Nearby ZIP codes are in USDA hardiness zone 7a.
- Apr 22Last spring frost (median)50% chance of 32°F after this date
- May 7Safer planting date10% chance of 32°F after this date
- Oct 9First fall frost (median)50% chance of 32°F by this date
- 168 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 21 | May 5 | May 21 |
| 32°F | Apr 7 | Apr 22 | May 7 |
| 28°F | Mar 18 | Apr 6 | Apr 23 |
| 24°F | Feb 27 | Mar 16 | Apr 6 |
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 16 | Sep 30 | Oct 12 |
| 32°F | Sep 26 | Oct 9 | Oct 23 |
| 28°F | Oct 6 | Oct 21 | Nov 4 |
| 24°F | Oct 19 | Nov 1 | Nov 20 |
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 | 122 days | 145 days | 163 days |
| 32°F | 149 days | 168 days | 187 days |
| 28°F | 175 days | 196 days | 219 days |
| 24°F | 201 days | 230 days | 255 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 |
|---|---|---|---|
| 83655 | 7a | 0 to 5°F | 18 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 USC00356294, at 44.0439, -116.9717, elevation 654 m (2,145 ft).
- Data quality: Representative (10+ years), 17 years of freeze data.
- Average days per year at or below 32°F: 150.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Ontario Muni Airport (4 km)
- Malheur Branch Exp. Station (8 km)
- Nyssa (19 km)
- Vale (23 km)
- Huntington (41 km)
- Owyhee Dam (49 km)
- Westfall (60 km)
- Rockville 5 N (77 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.