Henry, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 5.2 °C (low) to 16.5 °C (high). Annual precipitation averages 956.3 Millimeters. 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 | -8.7 °C | 0.2 °C | 50.8 mm |
| February | -6.8 °C | 2.7 °C | 47.75 mm |
| March | -1.4 °C | 9.6 °C | 64.52 mm |
| April | 4.4 °C | 17.2 °C | 95.5 mm |
| May | 10.7 °C | 23.2 °C | 119.38 mm |
| June | 16.1 °C | 28.1 °C | 106.93 mm |
| July | 18.1 °C | 29.8 °C | 97.79 mm |
| August | 17 °C | 28.9 °C | 93.22 mm |
| September | 12.5 °C | 25.8 °C | 86.61 mm |
| October | 6.1 °C | 18.8 °C | 76.96 mm |
| November | -0.1 °C | 10.2 °C | 65.53 mm |
| December | -5.5 °C | 3.1 °C | 51.31 mm |
| Annual | 5.2 °C | 16.5 °C | 956.3 mm |
| 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 : -23.3°C to -20.6°C |
| Plant Hardiness Zone - 2012 | Zone 5b : -26.1°C to -23.3°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |