Northport, Maine has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 3.1 °C (low) to 12.5 °C (high). Annual precipitation averages 1242.6 Millimeters. Northport is located in USDA Plant Hardiness Zone 5b. 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 | -10.4 °C | -0.7 °C | 101.6 mm |
| February | -9.7 °C | 0.4 °C | 82.8 mm |
| March | -4.8 °C | 4.4 °C | 99.06 mm |
| April | 1.2 °C | 10.6 °C | 112.52 mm |
| May | 6.8 °C | 17.1 °C | 97.28 mm |
| June | 11.8 °C | 21.8 °C | 110.24 mm |
| July | 15.5 °C | 25.2 °C | 79.76 mm |
| August | 15.2 °C | 24.9 °C | 82.3 mm |
| September | 11.4 °C | 20.8 °C | 100.84 mm |
| October | 5.6 °C | 14.1 °C | 139.7 mm |
| November | 0.1 °C | 8.3 °C | 119.13 mm |
| December | -6.1 °C | 2.6 °C | 117.35 mm |
| Annual | 3.1 °C | 12.5 °C | 1242.58 mm |
| 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 5b : -26.1°C to -23.3°C |
| Plant Hardiness Zone - 2012 | Zone 5b : -26.1°C to -23.3°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |