Westborough, Massachusetts has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 3.8 °C (low) to 15.5 °C (high). Annual precipitation averages 1247.9 Millimeters. Westborough is located in USDA Plant Hardiness Zone 6b. 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 | -8.7 °C | 1.8 °C | 96.77 mm |
| February | -7.9 °C | 3.3 °C | 85.34 mm |
| March | -3.6 °C | 7.6 °C | 115.57 mm |
| April | 2.2 °C | 14.6 °C | 109.98 mm |
| May | 8.1 °C | 20.5 °C | 90.17 mm |
| June | 13.3 °C | 25.2 °C | 107.95 mm |
| July | 16.5 °C | 28.3 °C | 95.5 mm |
| August | 15.6 °C | 27.5 °C | 104.14 mm |
| September | 11.1 °C | 23.7 °C | 99.57 mm |
| October | 4.7 °C | 17.1 °C | 123.95 mm |
| November | -0.6 °C | 10.8 °C | 98.81 mm |
| December | -5.2 °C | 5 °C | 120.14 mm |
| Annual | 3.8 °C | 15.5 °C | 1247.89 mm |
| 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 6b : -20.6°C to -17.8°C |
| Plant Hardiness Zone - 2012 | Zone 6a : -23.3°C to -20.6°C |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |