Stonington, Connecticut has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 44.5 °F (low) to 59.1 °F (high). Annual precipitation averages 47.3 Inches. Stonington 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 | 24.1 °F | 38.6 °F | 3.83 in. |
| February | 25.2 °F | 39.8 °F | 3.28 in. |
| March | 30.9 °F | 45.9 °F | 4.83 in. |
| April | 39.9 °F | 55.6 °F | 4.43 in. |
| May | 49.1 °F | 64.5 °F | 3.51 in. |
| June | 58.6 °F | 73.5 °F | 3.74 in. |
| July | 65.2 °F | 79.4 °F | 3.06 in. |
| August | 64.6 °F | 78.4 °F | 3.77 in. |
| September | 58.6 °F | 73.1 °F | 3.8 in. |
| October | 48.4 °F | 62.9 °F | 4.57 in. |
| November | 38.9 °F | 53.5 °F | 3.88 in. |
| December | 30.6 °F | 44.3 °F | 4.63 in. |
| Annual | 44.5 °F | 59.1 °F | 47.33 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 7a : 0°F to 5°F |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |