Henderson, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 4.4 °C (low) to 16.5 °C (high). Annual precipitation averages 879.9 Millimeters. Henderson 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. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -10.6 °C | 0.1 °C | 20.07 mm |
| February | -8.4 °C | 2.8 °C | 24.38 mm |
| March | -2.3 °C | 10.2 °C | 45.97 mm |
| April | 3.7 °C | 17.2 °C | 85.85 mm |
| May | 10.6 °C | 22.9 °C | 138.43 mm |
| June | 16.6 °C | 28.2 °C | 132.59 mm |
| July | 18.7 °C | 30.1 °C | 100.08 mm |
| August | 17.2 °C | 29.2 °C | 98.3 mm |
| September | 11.8 °C | 25.7 °C | 87.63 mm |
| October | 4.9 °C | 18.6 °C | 72.9 mm |
| November | -2.1 °C | 9.8 °C | 40.64 mm |
| December | -7.6 °C | 2.7 °C | 33.02 mm |
| Annual | 4.4 °C | 16.5 °C | 879.86 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 5b : -26.1°C to -23.3°C |
| Plant Hardiness Zone - 2012 | Zone 5a : -28.9°C to -26.1°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |