South Deerfield, Massachusetts has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 2.8 °C (low) to 15.1 °C (high). Annual precipitation averages 1238.8 Millimeters. South Deerfield is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around May 11 - May 20 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -10.1 °C | 0.7 °C | 87.38 mm |
| February | -9.4 °C | 2.4 °C | 78.74 mm |
| March | -4.7 °C | 7.2 °C | 93.47 mm |
| April | 1.3 °C | 14.7 °C | 99.31 mm |
| May | 7.3 °C | 21 °C | 96.01 mm |
| June | 12.7 °C | 25.7 °C | 119.89 mm |
| July | 15.6 °C | 28.6 °C | 106.43 mm |
| August | 14.6 °C | 27.6 °C | 112.27 mm |
| September | 10.2 °C | 23.7 °C | 119.13 mm |
| October | 3.8 °C | 16.2 °C | 125.48 mm |
| November | -1.7 °C | 9.5 °C | 91.69 mm |
| December | -6.3 °C | 3.6 °C | 108.97 mm |
| Annual | 2.8 °C | 15.1 °C | 1238.77 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 11 - May 20 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 6a : -23.3°C to -20.6°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 |