Hennepin, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 40.9 °F (low) to 61.3 °F (high). Annual precipitation averages 36.8 Inches. 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 | 15.7 °F | 31.9 °F | 1.77 in. |
| February | 19.3 °F | 36.4 °F | 1.79 in. |
| March | 29.1 °F | 48.8 °F | 2.42 in. |
| April | 39.6 °F | 62.7 °F | 3.45 in. |
| May | 50.8 °F | 73.7 °F | 4.48 in. |
| June | 60.5 °F | 82.3 °F | 4.38 in. |
| July | 64.0 °F | 85.4 °F | 3.85 in. |
| August | 62.1 °F | 83.7 °F | 3.95 in. |
| September | 53.9 °F | 78.0 °F | 3.5 in. |
| October | 42.4 °F | 65.6 °F | 2.88 in. |
| November | 31.5 °F | 50.0 °F | 2.42 in. |
| December | 21.6 °F | 37.1 °F | 1.93 in. |
| Annual | 40.9 °F | 61.3 °F | 36.82 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 5b : -15°F to -10°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 |