Southborough, Massachusetts has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 39 °F (low) to 59.7 °F (high). Annual precipitation averages 48.9 Inches. 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 | 16.5 °F | 35.3 °F | 3.85 in. |
| February | 18.0 °F | 38.0 °F | 3.39 in. |
| March | 25.8 °F | 45.6 °F | 4.59 in. |
| April | 36.1 °F | 58.2 °F | 4.33 in. |
| May | 46.5 °F | 68.6 °F | 3.54 in. |
| June | 55.9 °F | 77.1 °F | 4.26 in. |
| July | 61.7 °F | 82.8 °F | 3.67 in. |
| August | 60.2 °F | 81.4 °F | 3.93 in. |
| September | 52.0 °F | 74.7 °F | 3.82 in. |
| October | 40.6 °F | 62.6 °F | 4.78 in. |
| November | 31.2 °F | 51.5 °F | 3.91 in. |
| December | 22.9 °F | 41.1 °F | 4.85 in. |
| Annual | 39 °F | 59.7 °F | 48.92 in. |
| 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 : -5°F to 0°F |
| Plant Hardiness Zone - 2012 | Zone 6a : -10°F to -5°F |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |