Rockville, Connecticut has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 4 °C (low) to 15.2 °C (high). Annual precipitation averages 1212.6 Millimeters. Rockville 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 | -8.3 °C | 1.7 °C | 86.11 mm |
| February | -7.6 °C | 3.1 °C | 75.69 mm |
| March | -3.2 °C | 7.5 °C | 105.16 mm |
| April | 2.6 °C | 14.4 °C | 101.35 mm |
| May | 8.1 °C | 20.4 °C | 91.95 mm |
| June | 13.3 °C | 25.1 °C | 108.71 mm |
| July | 16.3 °C | 27.9 °C | 103.12 mm |
| August | 15.4 °C | 27.1 °C | 106.68 mm |
| September | 11.3 °C | 23.3 °C | 112.01 mm |
| October | 4.9 °C | 16.7 °C | 119.89 mm |
| November | -0.3 °C | 10.4 °C | 93.22 mm |
| December | -4.7 °C | 4.8 °C | 108.71 mm |
| Annual | 4 °C | 15.2 °C | 1212.6 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 6b : -20.6°C to -17.8°C |
| Plant Hardiness Zone - 2012 | Zone 6a : -23.3°C to -20.6°C |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |