Millbury, Massachusetts has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 38.2 °F (low) to 58.9 °F (high). Annual precipitation averages 49.5 Inches. Millbury is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 15.8 °F | 34.7 °F | 3.81 in. |
| February | 16.9 °F | 37.3 °F | 3.34 in. |
| March | 24.9 °F | 44.9 °F | 4.59 in. |
| April | 35.2 °F | 57.7 °F | 4.38 in. |
| May | 46.0 °F | 68.3 °F | 3.59 in. |
| June | 55.2 °F | 76.5 °F | 4.22 in. |
| July | 61.0 °F | 81.9 °F | 3.86 in. |
| August | 59.3 °F | 80.3 °F | 4.16 in. |
| September | 51.4 °F | 73.5 °F | 4.06 in. |
| October | 40.2 °F | 61.5 °F | 4.99 in. |
| November | 30.6 °F | 50.5 °F | 3.83 in. |
| December | 22.2 °F | 40.2 °F | 4.65 in. |
| Annual | 38.2 °F | 58.9 °F | 49.48 in. |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 125-150 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 |