Penobscot, Maine has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 1.8 °C (low) to 12.5 °C (high). Annual precipitation averages 1226.6 Millimeters. Penobscot is located in USDA Plant Hardiness Zone 5b. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -11.9 °C | -1.4 °C | 98.04 mm |
| February | -11 °C | 0.1 °C | 82.8 mm |
| March | -5.7 °C | 4.3 °C | 102.87 mm |
| April | 0.2 °C | 10.9 °C | 109.98 mm |
| May | 5.8 °C | 17.3 °C | 96.27 mm |
| June | 10.9 °C | 22.3 °C | 104.65 mm |
| July | 14.4 °C | 25.6 °C | 81.79 mm |
| August | 13.7 °C | 25.2 °C | 82.3 mm |
| September | 9.7 °C | 21.1 °C | 97.28 mm |
| October | 3.9 °C | 14.3 °C | 132.59 mm |
| November | -1.2 °C | 7.8 °C | 118.87 mm |
| December | -7.4 °C | 1.9 °C | 119.13 mm |
| Annual | 1.8 °C | 12.5 °C | 1226.57 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | May 1 - May 10 |
| 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 |