Shirley, Massachusetts has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 3.4 °C (low) to 15.4 °C (high). Annual precipitation averages 1243.3 Millimeters. Shirley 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 | -9.5 °C | 1.2 °C | 93.98 mm |
| February | -8.5 °C | 2.8 °C | 86.36 mm |
| March | -4 °C | 7.2 °C | 111.76 mm |
| April | 1.9 °C | 14.6 °C | 103.89 mm |
| May | 7.9 °C | 20.7 °C | 95.25 mm |
| June | 13.2 °C | 25.6 °C | 112.52 mm |
| July | 16.4 °C | 28.8 °C | 95.76 mm |
| August | 15.4 °C | 27.8 °C | 99.57 mm |
| September | 10.8 °C | 23.9 °C | 103.89 mm |
| October | 4.3 °C | 16.9 °C | 125.73 mm |
| November | -1 °C | 10.3 °C | 99.82 mm |
| December | -5.8 °C | 4.4 °C | 114.81 mm |
| Annual | 3.4 °C | 15.4 °C | 1243.34 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 |