Loudon, New Hampshire has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 36.1 °F (low) to 57.3 °F (high). Annual precipitation averages 45.4 Inches. Loudon 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 | 11.9 °F | 31.0 °F | 2.97 in. |
| February | 13.5 °F | 34.2 °F | 3.09 in. |
| March | 22.2 °F | 42.4 °F | 3.58 in. |
| April | 33.4 °F | 56.0 °F | 3.77 in. |
| May | 44.4 °F | 68.0 °F | 3.67 in. |
| June | 54.1 °F | 76.6 °F | 4.18 in. |
| July | 59.6 °F | 81.9 °F | 4.06 in. |
| August | 57.7 °F | 80.6 °F | 3.76 in. |
| September | 50.1 °F | 73.0 °F | 3.93 in. |
| October | 38.4 °F | 59.9 °F | 4.81 in. |
| November | 28.9 °F | 47.7 °F | 3.51 in. |
| December | 19.4 °F | 36.8 °F | 4.1 in. |
| Annual | 36.1 °F | 57.3 °F | 45.43 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 | Moderate Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |