Harvard, Massachusetts has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 3.6 °C (low) to 15.2 °C (high). Annual precipitation averages 1242.6 Millimeters. Harvard is located in USDA Plant Hardiness Zone 6a. 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 | -9.2 °C | 1.3 °C | 92.96 mm |
| February | -8.3 °C | 2.8 °C | 86.11 mm |
| March | -3.8 °C | 7.1 °C | 111.25 mm |
| April | 2.1 °C | 14.4 °C | 105.92 mm |
| May | 8.1 °C | 20.4 °C | 95.5 mm |
| June | 13.3 °C | 25.2 °C | 112.78 mm |
| July | 16.5 °C | 28.4 °C | 95.5 mm |
| August | 15.6 °C | 27.6 °C | 101.35 mm |
| September | 11 °C | 23.7 °C | 102.36 mm |
| October | 4.6 °C | 16.7 °C | 124.46 mm |
| November | -0.8 °C | 10.4 °C | 98.3 mm |
| December | -5.5 °C | 4.5 °C | 116.08 mm |
| Annual | 3.6 °C | 15.2 °C | 1242.57 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 1 - May 10 |
| 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 |