Iola, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 7 °C (low) to 18.4 °C (high). Annual precipitation averages 1145 Millimeters. Iola is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around Apr. 1 - Apr. 10 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -5.6 °C | 3.3 °C | 79.25 mm |
| February | -3.9 °C | 6.1 °C | 63.25 mm |
| March | 0.9 °C | 11.9 °C | 91.19 mm |
| April | 6.7 °C | 18.9 °C | 121.41 mm |
| May | 12.7 °C | 24.3 °C | 126.75 mm |
| June | 17.6 °C | 29.2 °C | 123.44 mm |
| July | 19.2 °C | 30.8 °C | 106.43 mm |
| August | 17.9 °C | 30.3 °C | 88.39 mm |
| September | 13.4 °C | 27.1 °C | 83.31 mm |
| October | 7.2 °C | 20.5 °C | 86.36 mm |
| November | 1.5 °C | 12.3 °C | 99.31 mm |
| December | -3.1 °C | 5.8 °C | 75.95 mm |
| Annual | 7 °C | 18.4 °C | 1145.04 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 6b : -20.6°C to -17.8°C |
| Plant Hardiness Zone - 2012 | Zone 6a : -23.3°C to -20.6°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |