Crystal Lake, Connecticut has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 38.5 °F (low) to 58.3 °F (high). Annual precipitation averages 49.1 Inches. Crystal Lake is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 17.0 °F | 34.3 °F | 3.4 in. |
| February | 17.7 °F | 36.6 °F | 3.06 in. |
| March | 25.5 °F | 44.3 °F | 4.13 in. |
| April | 35.5 °F | 56.9 °F | 4.1 in. |
| May | 45.5 °F | 67.6 °F | 3.61 in. |
| June | 54.9 °F | 75.8 °F | 4.49 in. |
| July | 60.6 °F | 81.0 °F | 4.04 in. |
| August | 58.7 °F | 79.3 °F | 4.49 in. |
| September | 51.6 °F | 72.6 °F | 4.57 in. |
| October | 40.3 °F | 60.9 °F | 5.01 in. |
| November | 31.2 °F | 49.9 °F | 3.73 in. |
| December | 23.4 °F | 40.0 °F | 4.42 in. |
| Annual | 38.5 °F | 58.3 °F | 49.05 in. |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 6b : -5°F to 0°F |
| Plant Hardiness Zone - 2012 | Zone 6a : -10°F to -5°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |