Troy, New Hampshire has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 2 °C (low) to 13.5 °C (high). Annual precipitation averages 1261.1 Millimeters. Troy is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around May 21 - May 31 through the first frost around Sep. 21 - Sep. 30.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -10.8 °C | -0.6 °C | 97.28 mm |
| February | -9.9 °C | 1.1 °C | 83.31 mm |
| March | -5.7 °C | 5.3 °C | 96.52 mm |
| April | 0.6 °C | 12.8 °C | 96.52 mm |
| May | 6.3 °C | 19.6 °C | 99.06 mm |
| June | 11.7 °C | 24.2 °C | 119.13 mm |
| July | 14.6 °C | 26.9 °C | 110.74 mm |
| August | 13.2 °C | 25.9 °C | 110.24 mm |
| September | 9 °C | 21.6 °C | 111.25 mm |
| October | 3.5 °C | 14.8 °C | 130.81 mm |
| November | -1.8 °C | 8.3 °C | 97.03 mm |
| December | -6.9 °C | 2.4 °C | 109.22 mm |
| Annual | 2 °C | 13.5 °C | 1261.11 mm |
| Average First Frost Date | Sep. 21 - Sep. 30 |
| Average Last Frost Date | May 21 - May 31 |
| 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 | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |