Winter Harbor, Maine has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 38.4 °F (low) to 53.2 °F (high). Annual precipitation averages 52.9 Inches. Winter Harbor is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 17.9 °F | 31.7 °F | 4.58 in. |
| February | 18.8 °F | 32.9 °F | 3.82 in. |
| March | 25.2 °F | 39.0 °F | 4.71 in. |
| April | 34.7 °F | 49.2 °F | 4.44 in. |
| May | 43.1 °F | 59.5 °F | 4.34 in. |
| June | 51.3 °F | 68.7 °F | 4.13 in. |
| July | 56.9 °F | 74.4 °F | 3.21 in. |
| August | 57.3 °F | 74.2 °F | 2.96 in. |
| September | 52.3 °F | 67.3 °F | 4.06 in. |
| October | 43.6 °F | 56.7 °F | 5.64 in. |
| November | 34.8 °F | 46.7 °F | 5.46 in. |
| December | 24.8 °F | 37.8 °F | 5.53 in. |
| Annual | 38.4 °F | 53.2 °F | 52.88 in. |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 6a : -10°F to -5°F |
| Plant Hardiness Zone - 2012 | Zone 5b : -15°F to -10°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |