Cohasset, Massachusetts has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 6.5 °C (low) to 15 °C (high). Annual precipitation averages 1338.1 Millimeters. Cohasset is located in USDA Plant Hardiness Zone 7a. 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 | -4.8 °C | 3.1 °C | 109.47 mm |
| February | -4.2 °C | 4.1 °C | 104.14 mm |
| March | -0.9 °C | 7.2 °C | 145.8 mm |
| April | 4.1 °C | 13.1 °C | 118.11 mm |
| May | 9.4 °C | 18.5 °C | 92.46 mm |
| June | 14.4 °C | 23.7 °C | 95.76 mm |
| July | 17.9 °C | 26.9 °C | 88.9 mm |
| August | 17.5 °C | 26.3 °C | 95.5 mm |
| September | 14.1 °C | 22.6 °C | 104.14 mm |
| October | 8.4 °C | 16.8 °C | 135.38 mm |
| November | 3.3 °C | 11.1 °C | 118.62 mm |
| December | -1.4 °C | 6.2 °C | 129.79 mm |
| Annual | 6.5 °C | 15 °C | 1338.07 mm |
| 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 7a : -17.8°C to -15°C |
| Plant Hardiness Zone - 2012 | Zone 6b : -20.6°C to -17.8°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |