Chillicothe, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 4.9 °C (low) to 15.9 °C (high). Annual precipitation averages 967.7 Millimeters. Chillicothe 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 | -9.9 °C | -0.7 °C | 33.02 mm |
| February | -8.1 °C | 1.8 °C | 39.62 mm |
| March | -2 °C | 9.6 °C | 56.64 mm |
| April | 4.5 °C | 16.6 °C | 96.77 mm |
| May | 11.1 °C | 22.4 °C | 129.54 mm |
| June | 16.9 °C | 28 °C | 137.67 mm |
| July | 18.5 °C | 30 °C | 107.19 mm |
| August | 17.5 °C | 28.7 °C | 100.33 mm |
| September | 12.3 °C | 24.7 °C | 100.33 mm |
| October | 5.6 °C | 18.1 °C | 71.12 mm |
| November | -1 °C | 9.1 °C | 55.12 mm |
| December | -6.6 °C | 2.4 °C | 40.39 mm |
| Annual | 4.9 °C | 15.9 °C | 967.74 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 |