Henry, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 41.4 °F (low) to 61.6 °F (high). Annual precipitation averages 37.7 Inches. Henry is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 16.3 °F | 32.3 °F | 2.0 in. |
| February | 19.8 °F | 36.8 °F | 1.88 in. |
| March | 29.5 °F | 49.2 °F | 2.54 in. |
| April | 40.0 °F | 62.9 °F | 3.76 in. |
| May | 51.2 °F | 73.7 °F | 4.7 in. |
| June | 60.9 °F | 82.5 °F | 4.21 in. |
| July | 64.6 °F | 85.6 °F | 3.85 in. |
| August | 62.6 °F | 84.1 °F | 3.67 in. |
| September | 54.5 °F | 78.4 °F | 3.41 in. |
| October | 42.9 °F | 65.8 °F | 3.03 in. |
| November | 31.9 °F | 50.3 °F | 2.58 in. |
| December | 22.1 °F | 37.5 °F | 2.02 in. |
| Annual | 41.4 °F | 61.6 °F | 37.65 in. |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 6a : -10°F to -5°F |
| Plant Hardiness Zone - 2012 | Zone 5b : -15°F to -10°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |