Dalton, Massachusetts has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 1.8 °C (low) to 13.4 °C (high). Annual precipitation averages 1216.9 Millimeters. Dalton is located in USDA Plant Hardiness Zone 5b. The growing season typically runs from the last frost around May 11 - May 20 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -10.9 °C | -0.7 °C | 83.57 mm |
| February | -10.2 °C | 1.1 °C | 71.63 mm |
| March | -5.8 °C | 5.2 °C | 92.46 mm |
| April | 0.3 °C | 12.8 °C | 93.22 mm |
| May | 6.2 °C | 19.4 °C | 90.93 mm |
| June | 11.3 °C | 24 °C | 120.65 mm |
| July | 14.1 °C | 26.4 °C | 116.08 mm |
| August | 13.4 °C | 25.3 °C | 111 mm |
| September | 9 °C | 21.6 °C | 125.22 mm |
| October | 3 °C | 14.9 °C | 121.41 mm |
| November | -2.1 °C | 8.2 °C | 86.61 mm |
| December | -6.9 °C | 2.3 °C | 104.14 mm |
| Annual | 1.8 °C | 13.4 °C | 1216.92 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 11 - May 20 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 5b : -26.1°C to -23.3°C |
| Plant Hardiness Zone - 2012 | Zone 5a : -28.9°C to -26.1°C |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |