Bantam, Connecticut has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 3.5 °C (low) to 14.8 °C (high). Annual precipitation averages 1303.8 Millimeters. Bantam 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 °C | 1.2 °C | 88.65 mm |
| February | -8 °C | 2.8 °C | 76.2 mm |
| March | -4.1 °C | 7.2 °C | 108.71 mm |
| April | 1.8 °C | 14.4 °C | 98.55 mm |
| May | 7.6 °C | 20.4 °C | 105.41 mm |
| June | 12.8 °C | 24.8 °C | 117.09 mm |
| July | 15.7 °C | 27.5 °C | 118.87 mm |
| August | 15.1 °C | 26.6 °C | 124.21 mm |
| September | 11.1 °C | 22.5 °C | 118.87 mm |
| October | 4.7 °C | 16.1 °C | 133.86 mm |
| November | -0.6 °C | 9.8 °C | 98.81 mm |
| December | -5.4 °C | 3.7 °C | 114.55 mm |
| Annual | 3.5 °C | 14.8 °C | 1303.78 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 | Dfb - Humid Continental Mild Summer, Wet All Year |