Mount Vernon, Oregon has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from 35 °F (low) to 64 °F (high). Annual precipitation averages 12.2 Inches. Mount Vernon 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. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 23.9 °F | 43.0 °F | 1.0 in. |
| February | 25.2 °F | 47.3 °F | 0.7 in. |
| March | 29.0 °F | 54.3 °F | 1.2 in. |
| April | 33.0 °F | 60.4 °F | 1.41 in. |
| May | 39.2 °F | 69.4 °F | 1.87 in. |
| June | 44.7 °F | 77.6 °F | 1.32 in. |
| July | 50.0 °F | 89.5 °F | 0.47 in. |
| August | 48.3 °F | 89.1 °F | 0.44 in. |
| September | 41.6 °F | 80.1 °F | 0.43 in. |
| October | 33.8 °F | 65.5 °F | 1.05 in. |
| November | 27.9 °F | 50.1 °F | 1.18 in. |
| December | 22.9 °F | 41.3 °F | 1.1 in. |
| Annual | 35 °F | 64 °F | 12.17 in. |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 150-180 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 | Extreme Drought |
| Köppen Climate Classification | BSk - Cold Semi-Arid Climate |