Swanzey, New Hampshire has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 35 °F (low) to 57.2 °F (high). Annual precipitation averages 46 Inches. Swanzey is located in USDA Plant Hardiness Zone 5b. The growing season typically runs from the last frost around May 11 - May 20 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 11.3 °F | 31.2 °F | 3.27 in. |
| February | 12.6 °F | 34.4 °F | 2.86 in. |
| March | 21.3 °F | 42.7 °F | 3.4 in. |
| April | 32.7 °F | 56.1 °F | 3.53 in. |
| May | 43.5 °F | 67.9 °F | 3.74 in. |
| June | 52.9 °F | 76.5 °F | 4.31 in. |
| July | 58.0 °F | 81.6 °F | 4.31 in. |
| August | 56.1 °F | 80.0 °F | 4.15 in. |
| September | 48.1 °F | 72.4 °F | 4.09 in. |
| October | 37.2 °F | 59.8 °F | 4.88 in. |
| November | 27.7 °F | 47.4 °F | 3.53 in. |
| December | 18.8 °F | 36.6 °F | 3.94 in. |
| Annual | 35 °F | 57.2 °F | 46.01 in. |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 11 - May 20 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 5b : -15°F to -10°F |
| Plant Hardiness Zone - 2012 | Zone 5b : -15°F to -10°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |