Killingworth, Connecticut has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 41.8 °F (low) to 60.2 °F (high). Annual precipitation averages 51.6 Inches. Killingworth 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 | 20.8 °F | 36.7 °F | 3.99 in. |
| February | 21.9 °F | 39.1 °F | 3.43 in. |
| March | 29.0 °F | 46.6 °F | 4.78 in. |
| April | 38.8 °F | 58.6 °F | 4.57 in. |
| May | 48.2 °F | 68.5 °F | 3.9 in. |
| June | 57.7 °F | 77.5 °F | 4.57 in. |
| July | 63.6 °F | 82.7 °F | 3.74 in. |
| August | 62.2 °F | 81.3 °F | 4.25 in. |
| September | 54.9 °F | 74.2 °F | 4.46 in. |
| October | 43.6 °F | 62.9 °F | 5.15 in. |
| November | 34.3 °F | 52.0 °F | 4.11 in. |
| December | 26.7 °F | 42.2 °F | 4.68 in. |
| Annual | 41.8 °F | 60.2 °F | 51.63 in. |
| 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 : 0°F to 5°F |
| Plant Hardiness Zone - 2012 | Zone 6b : -5°F to 0°F |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |