Washington, New Hampshire has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 37.9 °F (low) to 54.1 °F (high). Annual precipitation averages 53.1 Inches. Washington 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 | 13.8 °F | 27.5 °F | 3.84 in. |
| February | 14.9 °F | 30.5 °F | 3.46 in. |
| March | 22.9 °F | 38.8 °F | 4.11 in. |
| April | 34.5 °F | 53.3 °F | 4.15 in. |
| May | 45.6 °F | 65.8 °F | 4.14 in. |
| June | 56.1 °F | 73.7 °F | 4.83 in. |
| July | 61.6 °F | 78.1 °F | 5.18 in. |
| August | 58.9 °F | 76.7 °F | 4.46 in. |
| September | 51.6 °F | 69.6 °F | 4.34 in. |
| October | 41.6 °F | 56.7 °F | 5.75 in. |
| November | 30.6 °F | 44.7 °F | 4.1 in. |
| December | 22.1 °F | 33.3 °F | 4.71 in. |
| Annual | 37.9 °F | 54.1 °F | 53.07 in. |
| 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 : -10°F to -5°F |
| Plant Hardiness Zone - 2012 | Zone 6a : -10°F to -5°F |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |