Plymouth, New Hampshire has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 33.9 °F (low) to 55.6 °F (high). Annual precipitation averages 45.6 Inches. Plymouth 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 | 9.6 °F | 29.0 °F | 3.15 in. |
| February | 10.7 °F | 32.1 °F | 2.83 in. |
| March | 20.1 °F | 40.8 °F | 3.34 in. |
| April | 31.9 °F | 54.2 °F | 3.62 in. |
| May | 42.4 °F | 67.0 °F | 3.69 in. |
| June | 51.8 °F | 75.6 °F | 4.19 in. |
| July | 56.8 °F | 80.3 °F | 4.4 in. |
| August | 54.7 °F | 78.8 °F | 3.86 in. |
| September | 47.2 °F | 71.5 °F | 3.61 in. |
| October | 36.5 °F | 58.2 °F | 4.97 in. |
| November | 27.6 °F | 45.5 °F | 3.81 in. |
| December | 17.8 °F | 34.5 °F | 4.11 in. |
| Annual | 33.9 °F | 55.6 °F | 45.58 in. |
| 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 : -15°F to -10°F |
| Plant Hardiness Zone - 2012 | Zone 5a : -20°F to -15°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |