Brookline, New Hampshire has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 37.4 °F (low) to 58.9 °F (high). Annual precipitation averages 48.2 Inches. Brookline is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 14.2 °F | 33.7 °F | 3.48 in. |
| February | 15.8 °F | 36.6 °F | 3.28 in. |
| March | 24.0 °F | 44.5 °F | 4.07 in. |
| April | 34.7 °F | 57.6 °F | 4.07 in. |
| May | 45.7 °F | 68.7 °F | 3.81 in. |
| June | 55.1 °F | 77.6 °F | 4.42 in. |
| July | 60.5 °F | 83.0 °F | 3.9 in. |
| August | 58.5 °F | 81.3 °F | 3.85 in. |
| September | 50.7 °F | 73.9 °F | 4.08 in. |
| October | 38.8 °F | 61.1 °F | 4.92 in. |
| November | 29.6 °F | 49.7 °F | 3.9 in. |
| December | 20.7 °F | 39.0 °F | 4.43 in. |
| Annual | 37.4 °F | 58.9 °F | 48.21 in. |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 6a : -10°F to -5°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 |