Hartland, Maine has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 32.9 °F (low) to 54.8 °F (high). Annual precipitation averages 45.9 Inches. Hartland is located in USDA Plant Hardiness Zone 5a. The growing season typically runs from the last frost around May 11 - May 20 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 6.1 °F | 27.2 °F | 3.51 in. |
| February | 7.4 °F | 30.7 °F | 2.87 in. |
| March | 18.2 °F | 39.7 °F | 3.66 in. |
| April | 30.6 °F | 53.1 °F | 3.98 in. |
| May | 41.8 °F | 66.1 °F | 3.44 in. |
| June | 51.6 °F | 74.6 °F | 4.26 in. |
| July | 57.3 °F | 79.9 °F | 3.57 in. |
| August | 55.4 °F | 78.8 °F | 3.57 in. |
| September | 47.4 °F | 71.4 °F | 3.81 in. |
| October | 36.6 °F | 57.9 °F | 4.75 in. |
| November | 27.0 °F | 44.9 °F | 4.24 in. |
| December | 15.2 °F | 33.4 °F | 4.24 in. |
| Annual | 32.9 °F | 54.8 °F | 45.9 in. |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 11 - May 20 |
| 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 | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |