Holliston, Massachusetts has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 4.2 °C (low) to 15.6 °C (high). Annual precipitation averages 1245.1 Millimeters. Holliston 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 | -8.2 °C | 2.3 °C | 98.81 mm |
| February | -7.3 °C | 3.7 °C | 85.6 mm |
| March | -3.1 °C | 7.8 °C | 116.33 mm |
| April | 2.6 °C | 14.7 °C | 111.76 mm |
| May | 8.2 °C | 20.4 °C | 88.65 mm |
| June | 13.4 °C | 25.1 °C | 109.22 mm |
| July | 16.7 °C | 28.3 °C | 90.68 mm |
| August | 15.9 °C | 27.6 °C | 100.58 mm |
| September | 11.6 °C | 23.8 °C | 97.79 mm |
| October | 5.3 °C | 17.1 °C | 122.17 mm |
| November | 0.1 °C | 11 °C | 100.58 mm |
| December | -4.6 °C | 5.3 °C | 122.94 mm |
| Annual | 4.2 °C | 15.6 °C | 1245.11 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 100-125 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 | Severe Drought |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |