Dedham, Massachusetts has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 40.7 °F (low) to 60.4 °F (high). Annual precipitation averages 50 Inches. Dedham is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 18.8 °F | 36.9 °F | 4.02 in. |
| February | 20.3 °F | 39.3 °F | 3.52 in. |
| March | 27.8 °F | 46.3 °F | 4.88 in. |
| April | 37.9 °F | 58.2 °F | 4.41 in. |
| May | 47.5 °F | 68.8 °F | 3.67 in. |
| June | 56.9 °F | 77.6 °F | 4.17 in. |
| July | 62.9 °F | 83.4 °F | 3.68 in. |
| August | 61.3 °F | 81.9 °F | 3.84 in. |
| September | 54.0 °F | 74.9 °F | 3.84 in. |
| October | 42.6 °F | 63.0 °F | 4.92 in. |
| November | 33.4 °F | 52.4 °F | 4.14 in. |
| December | 25.0 °F | 42.4 °F | 4.9 in. |
| Annual | 40.7 °F | 60.4 °F | 49.99 in. |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 6b : -5°F to 0°F |
| Plant Hardiness Zone - 2012 | Zone 6b : -5°F to 0°F |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |