Fairfax, Vermont has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 35.7 °F (low) to 54.7 °F (high). Annual precipitation averages 40.9 Inches. Fairfax is located in USDA Plant Hardiness Zone 5a. 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 | 8.5 °F | 26.9 °F | 2.47 in. |
| February | 10.0 °F | 29.8 °F | 2.03 in. |
| March | 19.9 °F | 38.8 °F | 2.6 in. |
| April | 33.0 °F | 53.2 °F | 3.31 in. |
| May | 45.4 °F | 67.0 °F | 3.71 in. |
| June | 55.0 °F | 75.2 °F | 4.39 in. |
| July | 60.2 °F | 79.7 °F | 4.32 in. |
| August | 58.3 °F | 78.7 °F | 4.11 in. |
| September | 50.7 °F | 71.0 °F | 3.87 in. |
| October | 39.7 °F | 57.5 °F | 4.03 in. |
| November | 29.4 °F | 44.9 °F | 3.07 in. |
| December | 17.8 °F | 33.3 °F | 2.96 in. |
| Annual | 35.7 °F | 54.7 °F | 40.87 in. |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 5a : -20°F to -15°F |
| Plant Hardiness Zone - 2012 | Zone 4b : -25°F to -20°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |