Cromwell, Connecticut has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 5.2 °C (low) to 16 °C (high). Annual precipitation averages 1286.2 Millimeters. Cromwell is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -6.9 °C | 2.4 °C | 95.76 mm |
| February | -6.2 °C | 3.8 °C | 83.31 mm |
| March | -2 °C | 8.2 °C | 112.01 mm |
| April | 3.6 °C | 15.2 °C | 106.43 mm |
| May | 9.2 °C | 21.2 °C | 96.27 mm |
| June | 14.4 °C | 25.9 °C | 123.44 mm |
| July | 17.5 °C | 29 °C | 105.92 mm |
| August | 16.6 °C | 28.1 °C | 105.66 mm |
| September | 12.5 °C | 24 °C | 113.28 mm |
| October | 6.2 °C | 17.3 °C | 131.57 mm |
| November | 0.8 °C | 11 °C | 99.31 mm |
| December | -3.7 °C | 5.4 °C | 113.28 mm |
| Annual | 5.2 °C | 16 °C | 1286.24 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| 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 | Dfa - Humid Continental Hot Summers With Year Around Precipitation |