Norwich, Connecticut has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 5.8 °C (low) to 16.7 °C (high). Annual precipitation averages 1279.2 Millimeters. Norwich 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 | -6.2 °C | 3.6 °C | 96.52 mm |
| February | -5.2 °C | 5.1 °C | 87.38 mm |
| March | -1.2 °C | 9.2 °C | 121.41 mm |
| April | 4.2 °C | 15.8 °C | 117.35 mm |
| May | 9.6 °C | 21.6 °C | 89.92 mm |
| June | 14.8 °C | 26.3 °C | 101.35 mm |
| July | 18.3 °C | 29.2 °C | 91.19 mm |
| August | 17.3 °C | 28.5 °C | 111.76 mm |
| September | 12.8 °C | 24.4 °C | 115.06 mm |
| October | 6.7 °C | 18.2 °C | 122.17 mm |
| November | 1.4 °C | 12.1 °C | 103.89 mm |
| December | -2.8 °C | 6.6 °C | 121.16 mm |
| Annual | 5.8 °C | 16.7 °C | 1279.16 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 | Moderate Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |