Hartland, Connecticut has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 3.5 °C (low) to 15.2 °C (high). Annual precipitation averages 1282 Millimeters. Hartland 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 | -9.1 °C | 1.1 °C | 93.22 mm |
| February | -8.4 °C | 2.8 °C | 81.03 mm |
| March | -3.8 °C | 7.3 °C | 99.31 mm |
| April | 2.1 °C | 14.8 °C | 93.98 mm |
| May | 7.9 °C | 20.9 °C | 107.7 mm |
| June | 13.2 °C | 25.6 °C | 122.94 mm |
| July | 16 °C | 28.3 °C | 116.59 mm |
| August | 14.9 °C | 27.3 °C | 105.66 mm |
| September | 10.8 °C | 23.3 °C | 125.73 mm |
| October | 4.6 °C | 16.6 °C | 131.57 mm |
| November | -0.7 °C | 9.9 °C | 97.03 mm |
| December | -5.3 °C | 4 °C | 107.19 mm |
| Annual | 3.5 °C | 15.2 °C | 1281.95 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 5b : -26.1°C to -23.3°C |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |