Chelsea, Massachusetts has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 43.4 °F (low) to 59.5 °F (high). Annual precipitation averages 49.4 Inches. Chelsea is located in USDA Plant Hardiness Zone 7a. The growing season typically runs from the last frost around Apr. 1 - Apr. 10 through the first frost around Nov. 11 - Nov. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 21.6 °F | 37.0 °F | 4.07 in. |
| February | 23.1 °F | 39.2 °F | 3.72 in. |
| March | 29.9 °F | 45.3 °F | 4.93 in. |
| April | 40.0 °F | 56.6 °F | 4.37 in. |
| May | 49.5 °F | 66.8 °F | 3.49 in. |
| June | 59.3 °F | 76.3 °F | 4.08 in. |
| July | 65.3 °F | 82.1 °F | 3.58 in. |
| August | 64.2 °F | 80.5 °F | 3.56 in. |
| September | 57.2 °F | 73.3 °F | 3.67 in. |
| October | 46.1 °F | 62.3 °F | 4.91 in. |
| November | 36.6 °F | 51.9 °F | 4.13 in. |
| December | 27.9 °F | 42.5 °F | 4.93 in. |
| Annual | 43.4 °F | 59.5 °F | 49.44 in. |
| Average First Frost Date | Nov. 11 - Nov. 20 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| Average Days With Frost | 75-100 Days |
| Plant Hardiness Zone | Zone 7a : 0°F to 5°F |
| Plant Hardiness Zone - 2012 | Zone 6b : -5°F to 0°F |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |