Charlemont, Massachusetts has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 1.4 °C (low) to 12.8 °C (high). Annual precipitation averages 1297.4 Millimeters. Charlemont is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around May 21 - May 31 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -11.3 °C | -0.9 °C | 91.69 mm |
| February | -10.7 °C | 0.6 °C | 84.84 mm |
| March | -6.3 °C | 4.9 °C | 103.63 mm |
| April | -0.1 °C | 11.8 °C | 102.87 mm |
| May | 5.9 °C | 18.3 °C | 106.68 mm |
| June | 10.9 °C | 23.2 °C | 123.95 mm |
| July | 13.9 °C | 26 °C | 112.78 mm |
| August | 12.9 °C | 25.1 °C | 102.87 mm |
| September | 8.8 °C | 21.2 °C | 128.02 mm |
| October | 2.7 °C | 14.1 °C | 130.56 mm |
| November | -2.4 °C | 7.7 °C | 96.01 mm |
| December | -7.4 °C | 1.7 °C | 113.54 mm |
| Annual | 1.4 °C | 12.8 °C | 1297.44 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 21 - May 31 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 6a : -23.3°C to -20.6°C |
| Plant Hardiness Zone - 2012 | Zone 5b : -26.1°C to -23.3°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |