Southborough, Massachusetts has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 3.9 °C (low) to 15.4 °C (high). Annual precipitation averages 1242.6 Millimeters. Southborough 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 | -8.6 °C | 1.8 °C | 97.79 mm |
| February | -7.8 °C | 3.3 °C | 86.11 mm |
| March | -3.4 °C | 7.6 °C | 116.59 mm |
| April | 2.3 °C | 14.6 °C | 109.98 mm |
| May | 8.1 °C | 20.3 °C | 89.92 mm |
| June | 13.3 °C | 25.1 °C | 108.2 mm |
| July | 16.5 °C | 28.2 °C | 93.22 mm |
| August | 15.7 °C | 27.4 °C | 99.82 mm |
| September | 11.1 °C | 23.7 °C | 97.03 mm |
| October | 4.8 °C | 17 °C | 121.41 mm |
| November | -0.4 °C | 10.8 °C | 99.31 mm |
| December | -5.1 °C | 5.1 °C | 123.19 mm |
| Annual | 3.9 °C | 15.4 °C | 1242.57 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| 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 | Severe Drought |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |