Fort Fairfield, Maine has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 30.4 °F (low) to 50.6 °F (high). Annual precipitation averages 43.1 Inches. Fort Fairfield is located in USDA Plant Hardiness Zone 4a. The growing season typically runs from the last frost around May 21 - May 31 through the first frost around Sep. 21 - Sep. 30.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 1.3 °F | 21.4 °F | 3.5 in. |
| February | 2.1 °F | 24.2 °F | 2.59 in. |
| March | 14.1 °F | 34.1 °F | 2.91 in. |
| April | 28.6 °F | 48.0 °F | 3.31 in. |
| May | 40.3 °F | 63.3 °F | 3.59 in. |
| June | 49.7 °F | 72.5 °F | 4.12 in. |
| July | 56.0 °F | 77.4 °F | 4.38 in. |
| August | 53.7 °F | 76.2 °F | 3.86 in. |
| September | 46.4 °F | 68.1 °F | 3.63 in. |
| October | 35.4 °F | 54.0 °F | 3.98 in. |
| November | 25.3 °F | 40.1 °F | 3.42 in. |
| December | 12.2 °F | 28.4 °F | 3.8 in. |
| Annual | 30.4 °F | 50.6 °F | 43.09 in. |
| Average First Frost Date | Sep. 21 - Sep. 30 |
| Average Last Frost Date | May 21 - May 31 |
| Average Days With Frost | Over 180 Days |
| Plant Hardiness Zone | Zone 4a : -30°F to -25°F |
| Plant Hardiness Zone - 2012 | Zone 4a : -30°F to -25°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |