South Lancaster, Massachusetts has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 3.7 °C (low) to 15.4 °C (high). Annual precipitation averages 1263.1 Millimeters. South Lancaster 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. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -9.1 °C | 1.6 °C | 96.52 mm |
| February | -8.2 °C | 2.9 °C | 85.6 mm |
| March | -3.7 °C | 7.3 °C | 113.79 mm |
| April | 2.1 °C | 14.5 °C | 107.95 mm |
| May | 8.1 °C | 20.6 °C | 93.73 mm |
| June | 13.4 °C | 25.3 °C | 110.74 mm |
| July | 16.6 °C | 28.6 °C | 98.04 mm |
| August | 15.7 °C | 27.7 °C | 110.24 mm |
| September | 11 °C | 23.9 °C | 104.65 mm |
| October | 4.6 °C | 17.1 °C | 125.98 mm |
| November | -0.7 °C | 10.7 °C | 99.06 mm |
| December | -5.4 °C | 4.8 °C | 116.84 mm |
| Annual | 3.7 °C | 15.4 °C | 1263.14 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| 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 | Dfb - Humid Continental Mild Summer, Wet All Year |