Norwalk, Connecticut has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 6.9 °C (low) to 16.4 °C (high). Annual precipitation averages 1247.4 Millimeters. Norwalk is located in USDA Plant Hardiness Zone 7a. 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 | -4.9 °C | 3.8 °C | 100.84 mm |
| February | -4.2 °C | 4.8 °C | 73.91 mm |
| March | -0.5 °C | 8.8 °C | 104.65 mm |
| April | 5.1 °C | 15.2 °C | 99.57 mm |
| May | 10.3 °C | 20.8 °C | 94.23 mm |
| June | 15.7 °C | 25.7 °C | 126.75 mm |
| July | 18.9 °C | 28.7 °C | 93.47 mm |
| August | 18.4 °C | 27.9 °C | 106.17 mm |
| September | 14.4 °C | 24.5 °C | 119.63 mm |
| October | 8.4 °C | 18.1 °C | 110.49 mm |
| November | 3 °C | 12.1 °C | 101.6 mm |
| December | -1.4 °C | 6.8 °C | 116.08 mm |
| Annual | 6.9 °C | 16.4 °C | 1247.39 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 7a : -17.8°C to -15°C |
| Plant Hardiness Zone - 2012 | Zone 7a : -17.8°C to -15°C |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |