Winterport, Maine has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 34.3 °F (low) to 54.6 °F (high). Annual precipitation averages 48.4 Inches. Winterport 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 | 28.6 °F | 3.96 in. |
| February | 10.5 °F | 31.5 °F | 3.35 in. |
| March | 21.1 °F | 39.6 °F | 4.28 in. |
| April | 31.8 °F | 52.1 °F | 4.36 in. |
| May | 42.1 °F | 64.3 °F | 3.78 in. |
| June | 51.2 °F | 73.2 °F | 4.02 in. |
| July | 57.7 °F | 79.0 °F | 3.27 in. |
| August | 56.0 °F | 78.1 °F | 3.35 in. |
| September | 48.4 °F | 70.4 °F | 3.83 in. |
| October | 37.7 °F | 57.8 °F | 4.95 in. |
| November | 28.7 °F | 45.8 °F | 4.35 in. |
| December | 17.3 °F | 34.7 °F | 4.89 in. |
| Annual | 34.3 °F | 54.6 °F | 48.39 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 5b : -15°F to -10°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |