Sandown, New Hampshire has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 3.1 °C (low) to 14.8 °C (high). Annual precipitation averages 1190.5 Millimeters. Sandown 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 | -9.6 °C | 0.9 °C | 81.28 mm |
| February | -8.7 °C | 2.6 °C | 82.8 mm |
| March | -4.3 °C | 6.9 °C | 106.17 mm |
| April | 1.5 °C | 14.1 °C | 104.39 mm |
| May | 7.3 °C | 20.1 °C | 100.84 mm |
| June | 12.6 °C | 25 °C | 104.14 mm |
| July | 15.8 °C | 28.1 °C | 89.92 mm |
| August | 14.8 °C | 27.3 °C | 93.73 mm |
| September | 10.5 °C | 23.2 °C | 97.28 mm |
| October | 4.1 °C | 16.1 °C | 123.95 mm |
| November | -1 °C | 9.9 °C | 96.77 mm |
| December | -5.9 °C | 3.9 °C | 109.22 mm |
| Annual | 3.1 °C | 14.8 °C | 1190.49 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 6a : -23.3°C to -20.6°C |
| Plant Hardiness Zone - 2012 | Zone 5b : -26.1°C to -23.3°C |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |