Wellesley, Massachusetts has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 39.9 °F (low) to 60.3 °F (high). Annual precipitation averages 48.2 Inches. Wellesley is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 17.8 °F | 36.2 °F | 3.75 in. |
| February | 19.5 °F | 38.8 °F | 3.26 in. |
| March | 27.0 °F | 46.1 °F | 4.43 in. |
| April | 37.1 °F | 58.5 °F | 4.18 in. |
| May | 47.0 °F | 68.9 °F | 3.69 in. |
| June | 56.3 °F | 77.6 °F | 4.22 in. |
| July | 62.3 °F | 83.5 °F | 3.6 in. |
| August | 60.7 °F | 82.1 °F | 3.88 in. |
| September | 53.1 °F | 75.2 °F | 3.82 in. |
| October | 41.7 °F | 63.0 °F | 4.79 in. |
| November | 32.5 °F | 52.1 °F | 3.96 in. |
| December | 24.1 °F | 41.8 °F | 4.62 in. |
| Annual | 39.9 °F | 60.3 °F | 48.2 in. |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 6b : -5°F to 0°F |
| Plant Hardiness Zone - 2012 | Zone 6a : -10°F to -5°F |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |