Dennis, Massachusetts has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 44.1 °F (low) to 57.9 °F (high). Annual precipitation averages 48.2 Inches. Dennis is located in USDA Plant Hardiness Zone 7b. 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 | 24.6 °F | 38.4 °F | 4.33 in. |
| February | 25.5 °F | 39.2 °F | 3.67 in. |
| March | 30.6 °F | 44.2 °F | 4.67 in. |
| April | 39.1 °F | 52.8 °F | 4.4 in. |
| May | 48.3 °F | 62.5 °F | 3.41 in. |
| June | 57.6 °F | 71.5 °F | 3.45 in. |
| July | 64.7 °F | 78.4 °F | 2.84 in. |
| August | 64.0 °F | 77.6 °F | 3.33 in. |
| September | 57.7 °F | 71.9 °F | 4.18 in. |
| October | 47.6 °F | 61.7 °F | 4.64 in. |
| November | 38.5 °F | 52.3 °F | 4.06 in. |
| December | 30.7 °F | 44.0 °F | 5.18 in. |
| Annual | 44.1 °F | 57.9 °F | 48.16 in. |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 75-100 Days |
| Plant Hardiness Zone | Zone 7b : 5°F to 10°F |
| Plant Hardiness Zone - 2012 | Zone 7a : 0°F to 5°F |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |