Last frost date in Ontario, Oregon
April 22
Average last frost in spring. In an early year (1 in 10) it's over by April 7; in a late year (1 in 10) it comes after May 7.
October 9
Average first frost in fall. 1 year in 10 it comes by September 26.
Source: NOAA U.S. Climate Normals 1991–2020, station Ontario Ksrv (USC00356294), 1.3 miles from Ontario, elevation 2,145 ft. NOAA National Centers for Environmental Information. These are long-term averages, not a forecast.
| Early year | Average | Late year | |
|---|---|---|---|
| Last frost in spring | Apr 7 | Apr 22 | May 7 |
| First frost in fall | Sept 26 | Oct 9 | Oct 23 |
Frost-free days in an average year: 168
| Chance in a year | Average last in spring | Average first in fall | |
|---|---|---|---|
| Light frost (36°F) | Every year | May 5 | Sept 30 |
| Frost (32°F) | Every year | Apr 22 | Oct 9 |
| Hard freeze (28°F) | Every year | Apr 6 | Oct 21 |
Nights at 32°F or colder in an average year: 150
What to plant now in Ontario
- Spring planting calendar for an average last frost around April 20 Ontario: April 22
- Fall planting calendar for an average first frost around October 10 Ontario: October 9
Planting dates: USDA Home and Garden Bulletin No. 9 (1967), “Suburban and Farm Vegetable Gardens,” tables 4 and 5. How we match the table.
Nearby in Oregon
- Baker City 67 mi · last frost May 25
- La Grande 105 mi · last frost May 6
- Pendleton 145 mi · last frost Apr 22
- Hermiston 168 mi · last frost Apr 26
- Prineville 193 mi · last frost June 1
Updated