Henderson, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 39.9 °F (low) to 61.6 °F (high). Annual precipitation averages 34.6 Inches. 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 | 12.9 °F | 32.2 °F | 0.79 in. |
| February | 16.8 °F | 37.1 °F | 0.96 in. |
| March | 27.9 °F | 50.4 °F | 1.81 in. |
| April | 38.6 °F | 62.9 °F | 3.38 in. |
| May | 51.1 °F | 73.2 °F | 5.45 in. |
| June | 61.8 °F | 82.8 °F | 5.22 in. |
| July | 65.6 °F | 86.2 °F | 3.94 in. |
| August | 62.9 °F | 84.5 °F | 3.87 in. |
| September | 53.3 °F | 78.2 °F | 3.45 in. |
| October | 40.8 °F | 65.5 °F | 2.87 in. |
| November | 28.2 °F | 49.6 °F | 1.6 in. |
| December | 18.3 °F | 36.9 °F | 1.3 in. |
| Annual | 39.9 °F | 61.6 °F | 34.64 in. |
| 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 : -15°F to -10°F |
| Plant Hardiness Zone - 2012 | Zone 5a : -20°F to -15°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |