Bristol, New Hampshire has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 1.9 °C (low) to 13.8 °C (high). Annual precipitation averages 1179.3 Millimeters. Bristol 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. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -11.6 °C | -1.1 °C | 80.26 mm |
| February | -11.1 °C | 0.7 °C | 65.02 mm |
| March | -6.1 °C | 5.4 °C | 85.85 mm |
| April | 0.3 °C | 13.1 °C | 100.58 mm |
| May | 6.5 °C | 20.1 °C | 102.87 mm |
| June | 11.8 °C | 24.7 °C | 106.68 mm |
| July | 14.9 °C | 27.7 °C | 98.81 mm |
| August | 13.7 °C | 26.8 °C | 102.36 mm |
| September | 9.6 °C | 22.6 °C | 87.38 mm |
| October | 3.3 °C | 15.1 °C | 137.92 mm |
| November | -1.8 °C | 8.1 °C | 102.62 mm |
| December | -7.3 °C | 2.1 °C | 108.97 mm |
| Annual | 1.9 °C | 13.8 °C | 1179.32 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| 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 |