Franklin, New Hampshire has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 2.1 °C (low) to 14.4 °C (high). Annual precipitation averages 1147.6 Millimeters. Franklin 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 | -11.4 °C | -0.4 °C | 76.2 mm |
| February | -10.7 °C | 1.3 °C | 71.37 mm |
| March | -5.8 °C | 6.1 °C | 84.58 mm |
| April | 0.3 °C | 13.8 °C | 88.14 mm |
| May | 6.7 °C | 20.7 °C | 93.22 mm |
| June | 12.1 °C | 25.4 °C | 106.17 mm |
| July | 15.4 °C | 28.4 °C | 111.51 mm |
| August | 14.1 °C | 27.5 °C | 95 mm |
| September | 9.9 °C | 23.2 °C | 91.44 mm |
| October | 3.3 °C | 15.7 °C | 128.78 mm |
| November | -1.9 °C | 8.7 °C | 97.03 mm |
| December | -7.3 °C | 2.6 °C | 104.14 mm |
| Annual | 2.1 °C | 14.4 °C | 1147.58 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 |