Littleton, Massachusetts has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 3.5 °C (low) to 15.4 °C (high). Annual precipitation averages 1235.5 Millimeters. Littleton is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -9.3 °C | 1.5 °C | 91.95 mm |
| February | -8.3 °C | 2.9 °C | 86.61 mm |
| March | -3.9 °C | 7.3 °C | 111 mm |
| April | 2 °C | 14.6 °C | 107.44 mm |
| May | 7.8 °C | 20.6 °C | 96.52 mm |
| June | 13.1 °C | 25.4 °C | 112.78 mm |
| July | 16.3 °C | 28.7 °C | 93.98 mm |
| August | 15.3 °C | 27.8 °C | 98.3 mm |
| September | 10.8 °C | 23.9 °C | 99.31 mm |
| October | 4.3 °C | 16.9 °C | 122.94 mm |
| November | -0.9 °C | 10.6 °C | 97.54 mm |
| December | -5.6 °C | 4.7 °C | 117.09 mm |
| Annual | 3.5 °C | 15.4 °C | 1235.46 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 6a : -23.3°C to -20.6°C |
| Plant Hardiness Zone - 2012 | Zone 6a : -23.3°C to -20.6°C |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |