Sandwich, New Hampshire has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 0.5 °C (low) to 12.7 °C (high). Annual precipitation averages 1362 Millimeters. Sandwich is located in USDA Plant Hardiness Zone 5b. 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 | -13 °C | -1.9 °C | 94.49 mm |
| February | -12.3 °C | -0.4 °C | 86.11 mm |
| March | -7.2 °C | 4.4 °C | 101.09 mm |
| April | -0.8 °C | 11.9 °C | 110.49 mm |
| May | 5.2 °C | 19.1 °C | 108.46 mm |
| June | 10.3 °C | 23.6 °C | 125.98 mm |
| July | 13.1 °C | 26.3 °C | 128.78 mm |
| August | 12.1 °C | 25.6 °C | 115.57 mm |
| September | 7.9 °C | 21.3 °C | 106.43 mm |
| October | 2.1 °C | 13.9 °C | 146.05 mm |
| November | -2.7 °C | 7 °C | 114.3 mm |
| December | -8.5 °C | 1.1 °C | 124.21 mm |
| Annual | 0.5 °C | 12.7 °C | 1361.96 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 150-180 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 | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |