Sandown, New Hampshire has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 37.6 °F (low) to 58.7 °F (high). Annual precipitation averages 46.9 Inches. 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 | 14.7 °F | 33.7 °F | 3.2 in. |
| February | 16.4 °F | 36.6 °F | 3.26 in. |
| March | 24.2 °F | 44.4 °F | 4.18 in. |
| April | 34.7 °F | 57.3 °F | 4.11 in. |
| May | 45.2 °F | 68.1 °F | 3.97 in. |
| June | 54.7 °F | 77.0 °F | 4.1 in. |
| July | 60.4 °F | 82.5 °F | 3.54 in. |
| August | 58.6 °F | 81.1 °F | 3.69 in. |
| September | 50.9 °F | 73.7 °F | 3.83 in. |
| October | 39.4 °F | 61.0 °F | 4.88 in. |
| November | 30.2 °F | 49.8 °F | 3.81 in. |
| December | 21.3 °F | 39.0 °F | 4.3 in. |
| Annual | 37.6 °F | 58.7 °F | 46.87 in. |
| 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 : -10°F to -5°F |
| Plant Hardiness Zone - 2012 | Zone 5b : -15°F to -10°F |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |