Lexington, Massachusetts has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 4.1 °C (low) to 15.5 °C (high). Annual precipitation averages 1235.7 Millimeters. Lexington is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -8.3 °C | 1.9 °C | 96.77 mm |
| February | -7.3 °C | 3.4 °C | 87.63 mm |
| March | -3.3 °C | 7.9 °C | 116.84 mm |
| April | 2.4 °C | 14.6 °C | 106.17 mm |
| May | 8 °C | 20.3 °C | 92.96 mm |
| June | 13.2 °C | 25.2 °C | 106.43 mm |
| July | 16.5 °C | 28.5 °C | 93.47 mm |
| August | 15.7 °C | 27.7 °C | 95.76 mm |
| September | 11.4 °C | 23.8 °C | 94.49 mm |
| October | 5.2 °C | 16.9 °C | 122.43 mm |
| November | -0.1 °C | 10.9 °C | 101.6 mm |
| December | -4.7 °C | 5.1 °C | 121.16 mm |
| Annual | 4.1 °C | 15.5 °C | 1235.71 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| 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 | Dfb - Humid Continental Mild Summer, Wet All Year |