Mount Vernon, Maine has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 34.2 °F (low) to 54.2 °F (high). Annual precipitation averages 47.5 Inches. Mount Vernon is located in USDA Plant Hardiness Zone 5a. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 8.8 °F | 27.6 °F | 3.44 in. |
| February | 10.1 °F | 30.5 °F | 3.02 in. |
| March | 20.0 °F | 39.2 °F | 3.56 in. |
| April | 31.9 °F | 52.2 °F | 4.1 in. |
| May | 42.9 °F | 64.9 °F | 3.62 in. |
| June | 52.3 °F | 73.3 °F | 4.74 in. |
| July | 57.8 °F | 78.8 °F | 3.82 in. |
| August | 56.1 °F | 77.9 °F | 3.65 in. |
| September | 48.2 °F | 70.5 °F | 3.66 in. |
| October | 37.5 °F | 57.3 °F | 5.37 in. |
| November | 27.7 °F | 44.7 °F | 4.26 in. |
| December | 17.1 °F | 33.7 °F | 4.29 in. |
| Annual | 34.2 °F | 54.2 °F | 47.53 in. |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 5a : -20°F to -15°F |
| Plant Hardiness Zone - 2012 | Zone 5a : -20°F to -15°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |