Southbury, Connecticut has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 4.7 °C (low) to 15.8 °C (high). Annual precipitation averages 1288.3 Millimeters. Southbury 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. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -7.4 °C | 2.3 °C | 95.25 mm |
| February | -6.6 °C | 3.9 °C | 78.49 mm |
| March | -2.6 °C | 8.2 °C | 108.46 mm |
| April | 3.2 °C | 15.1 °C | 103.12 mm |
| May | 8.8 °C | 21.3 °C | 101.09 mm |
| June | 13.9 °C | 25.8 °C | 117.09 mm |
| July | 17.1 °C | 28.6 °C | 115.57 mm |
| August | 16.2 °C | 27.6 °C | 113.54 mm |
| September | 12.2 °C | 23.7 °C | 114.81 mm |
| October | 5.6 °C | 17.3 °C | 126.75 mm |
| November | 0.2 °C | 10.9 °C | 102.62 mm |
| December | -4.2 °C | 5.1 °C | 111.51 mm |
| Annual | 4.7 °C | 15.8 °C | 1288.3 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| 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 6b : -20.6°C to -17.8°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |