Hennepin, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 4.9 °C (low) to 16.3 °C (high). Annual precipitation averages 935.2 Millimeters. Hennepin is located in USDA Plant Hardiness Zone 5b. 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 | -9.1 °C | -0.1 °C | 44.96 mm |
| February | -7.1 °C | 2.4 °C | 45.47 mm |
| March | -1.6 °C | 9.3 °C | 61.47 mm |
| April | 4.2 °C | 17.1 °C | 87.63 mm |
| May | 10.4 °C | 23.2 °C | 113.79 mm |
| June | 15.8 °C | 27.9 °C | 111.25 mm |
| July | 17.8 °C | 29.7 °C | 97.79 mm |
| August | 16.7 °C | 28.7 °C | 100.33 mm |
| September | 12.2 °C | 25.6 °C | 88.9 mm |
| October | 5.8 °C | 18.7 °C | 73.15 mm |
| November | -0.3 °C | 10 °C | 61.47 mm |
| December | -5.8 °C | 2.8 °C | 49.02 mm |
| Annual | 4.9 °C | 16.3 °C | 935.23 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 5b : -26.1°C to -23.3°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 |