Mount Vernon, Oregon has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from 1.6 °C (low) to 17.8 °C (high). Annual precipitation averages 309.1 Millimeters. 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 | -4.5 °C | 6.1 °C | 25.4 mm |
| February | -3.8 °C | 8.5 °C | 17.78 mm |
| March | -1.7 °C | 12.4 °C | 30.48 mm |
| April | 0.6 °C | 15.8 °C | 35.81 mm |
| May | 4 °C | 20.8 °C | 47.5 mm |
| June | 7.1 °C | 25.3 °C | 33.53 mm |
| July | 10 °C | 31.9 °C | 11.94 mm |
| August | 9.1 °C | 31.7 °C | 11.18 mm |
| September | 5.3 °C | 26.7 °C | 10.92 mm |
| October | 1 °C | 18.6 °C | 26.67 mm |
| November | -2.3 °C | 10.1 °C | 29.97 mm |
| December | -5.1 °C | 5.2 °C | 27.94 mm |
| Annual | 1.6 °C | 17.8 °C | 309.12 mm |
| 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 : -17.8°C to -15°C |
| Plant Hardiness Zone - 2012 | Zone 6b : -20.6°C to -17.8°C |
| Current Drought Conditions | Extreme Drought |
| Köppen Climate Classification | BSk - Cold Semi-Arid Climate |