Ontario, Oregon has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from 39.3 °F (low) to 65 °F (high). Annual precipitation averages 9.4 Inches. Ontario is located in USDA Plant Hardiness Zone 7a. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 23.0 °F | 37.1 °F | 1.07 in. |
| February | 26.5 °F | 45.8 °F | 0.76 in. |
| March | 32.2 °F | 57.0 °F | 0.84 in. |
| April | 37.3 °F | 64.5 °F | 0.82 in. |
| May | 46.0 °F | 73.9 °F | 1.22 in. |
| June | 52.8 °F | 82.2 °F | 0.68 in. |
| July | 59.7 °F | 92.9 °F | 0.31 in. |
| August | 57.1 °F | 91.5 °F | 0.11 in. |
| September | 47.8 °F | 81.0 °F | 0.36 in. |
| October | 37.0 °F | 66.1 °F | 0.71 in. |
| November | 28.6 °F | 49.5 °F | 0.99 in. |
| December | 23.2 °F | 38.2 °F | 1.56 in. |
| Annual | 39.3 °F | 65 °F | 9.43 in. |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 7a : 0°F to 5°F |
| Plant Hardiness Zone - 2012 | Zone 6b : -5°F to 0°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | BSk - Cold Semi-Arid Climate |