Northfield, Massachusetts has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 2.4 °C (low) to 14.8 °C (high). Annual precipitation averages 1209.3 Millimeters. Northfield is located in USDA Plant Hardiness Zone 5b. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -10.7 °C | 0.2 °C | 90.42 mm |
| February | -10.1 °C | 2.1 °C | 78.49 mm |
| March | -5.1 °C | 6.8 °C | 94.74 mm |
| April | 0.8 °C | 14.2 °C | 93.73 mm |
| May | 7 °C | 20.8 °C | 91.95 mm |
| June | 12.4 °C | 25.7 °C | 114.81 mm |
| July | 15.2 °C | 28.6 °C | 104.9 mm |
| August | 14.3 °C | 27.7 °C | 108.2 mm |
| September | 9.8 °C | 23.4 °C | 107.95 mm |
| October | 3.4 °C | 16.1 °C | 125.22 mm |
| November | -1.7 °C | 9.2 °C | 93.47 mm |
| December | -6.7 °C | 3.2 °C | 105.41 mm |
| Annual | 2.4 °C | 14.8 °C | 1209.29 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 5b : -26.1°C to -23.3°C |
| Plant Hardiness Zone - 2012 | Zone 5b : -26.1°C to -23.3°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |