Kelley, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 3.6 °C (low) to 14.8 °C (high). Annual precipitation averages 944.6 Millimeters. Kelley 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. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -11.7 °C | -2.1 °C | 23.62 mm |
| February | -9.4 °C | 0.4 °C | 29.21 mm |
| March | -3.1 °C | 7.7 °C | 52.32 mm |
| April | 3.2 °C | 15.7 °C | 96.52 mm |
| May | 9.9 °C | 21.6 °C | 131.83 mm |
| June | 15.7 °C | 26.9 °C | 138.18 mm |
| July | 17.7 °C | 28.8 °C | 112.01 mm |
| August | 16.2 °C | 27.6 °C | 115.32 mm |
| September | 11.4 °C | 24.5 °C | 92.46 mm |
| October | 4.4 °C | 17.1 °C | 69.6 mm |
| November | -2.3 °C | 8.5 °C | 47.5 mm |
| December | -8.3 °C | 0.9 °C | 36.07 mm |
| Annual | 3.6 °C | 14.8 °C | 944.64 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| 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 |