Dedham, Maine has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 37.2 °F (low) to 52 °F (high). Annual precipitation averages 46.4 Inches. Dedham 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 | 12.9 °F | 25.2 °F | 3.59 in. |
| February | 14.2 °F | 29.5 °F | 2.88 in. |
| March | 20.5 °F | 37.7 °F | 3.85 in. |
| April | 34.3 °F | 49.9 °F | 4.07 in. |
| May | 45.4 °F | 61.6 °F | 3.65 in. |
| June | 54.7 °F | 70.6 °F | 3.96 in. |
| July | 60.8 °F | 76.4 °F | 3.34 in. |
| August | 59.6 °F | 75.7 °F | 3.4 in. |
| September | 52.0 °F | 68.2 °F | 3.77 in. |
| October | 41.0 °F | 55.5 °F | 5.0 in. |
| November | 30.8 °F | 42.4 °F | 4.35 in. |
| December | 19.7 °F | 31.2 °F | 4.51 in. |
| Annual | 37.2 °F | 52 °F | 46.37 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 5a : -20°F to -15°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |