Westwood, Massachusetts has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 4.7 °C (low) to 15.6 °C (high). Annual precipitation averages 1263.4 Millimeters. Westwood 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. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -7.6 °C | 2.4 °C | 102.36 mm |
| February | -6.7 °C | 3.8 °C | 87.88 mm |
| March | -2.6 °C | 7.8 °C | 123.7 mm |
| April | 3.1 °C | 14.4 °C | 112.78 mm |
| May | 8.5 °C | 20.2 °C | 91.44 mm |
| June | 13.7 °C | 25.1 °C | 104.65 mm |
| July | 17.1 °C | 28.3 °C | 91.19 mm |
| August | 16.2 °C | 27.5 °C | 98.55 mm |
| September | 12.2 °C | 23.6 °C | 96.27 mm |
| October | 5.8 °C | 16.9 °C | 125.22 mm |
| November | 0.7 °C | 11.1 °C | 105.66 mm |
| December | -4.1 °C | 5.5 °C | 123.7 mm |
| Annual | 4.7 °C | 15.6 °C | 1263.4 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 6b : -20.6°C to -17.8°C |
| Plant Hardiness Zone - 2012 | Zone 6b : -20.6°C to -17.8°C |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |