Littleton, New Hampshire has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from -0.1 °C (low) to 12.5 °C (high). Annual precipitation averages 972.6 Millimeters. Littleton is located in USDA Plant Hardiness Zone 4b. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Sep. 21 - Sep. 30.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -14.6 °C | -2.8 °C | 55.88 mm |
| February | -14.2 °C | -0.9 °C | 47.75 mm |
| March | -8.4 °C | 4.2 °C | 56.39 mm |
| April | -1.2 °C | 11.7 °C | 76.45 mm |
| May | 5.3 °C | 19.2 °C | 90.93 mm |
| June | 10.4 °C | 23.8 °C | 102.11 mm |
| July | 13.2 °C | 26.5 °C | 108.2 mm |
| August | 12.1 °C | 25.7 °C | 100.84 mm |
| September | 7.9 °C | 21.6 °C | 86.61 mm |
| October | 1.9 °C | 13.9 °C | 102.11 mm |
| November | -3.4 °C | 6.6 °C | 67.56 mm |
| December | -9.7 °C | 0.2 °C | 77.72 mm |
| Annual | -0.1 °C | 12.5 °C | 972.55 mm |
| Average First Frost Date | Sep. 21 - Sep. 30 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 4b : -31.7°C to -28.9°C |
| Plant Hardiness Zone - 2012 | Zone 4b : -31.7°C to -28.9°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |