Sleepy Hollow, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 39.5 °F (low) to 58.8 °F (high). Annual precipitation averages 39.6 Inches. Sleepy Hollow is located in USDA Plant Hardiness Zone 5b. 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 | 14.6 °F | 30.3 °F | 1.95 in. |
| February | 17.3 °F | 34.3 °F | 1.85 in. |
| March | 26.9 °F | 45.9 °F | 2.26 in. |
| April | 37.2 °F | 58.6 °F | 3.82 in. |
| May | 48.2 °F | 70.1 °F | 5.18 in. |
| June | 58.2 °F | 80.0 °F | 4.77 in. |
| July | 63.1 °F | 84.0 °F | 4.01 in. |
| August | 61.5 °F | 82.0 °F | 4.15 in. |
| September | 53.5 °F | 75.3 °F | 3.56 in. |
| October | 41.7 °F | 62.2 °F | 3.31 in. |
| November | 30.6 °F | 47.7 °F | 2.55 in. |
| December | 20.6 °F | 35.6 °F | 2.17 in. |
| Annual | 39.5 °F | 58.8 °F | 39.58 in. |
| 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 5b : -15°F to -10°F |
| Plant Hardiness Zone - 2012 | Zone 5b : -15°F to -10°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |