Roanoke, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 5 °C (low) to 16.5 °C (high). Annual precipitation averages 963.7 Millimeters. Roanoke 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 | -8.9 °C | 0.2 °C | 56.9 mm |
| February | -7.1 °C | 2.9 °C | 50.04 mm |
| March | -1.7 °C | 9.7 °C | 67.56 mm |
| April | 4.2 °C | 17.1 °C | 93.73 mm |
| May | 10.7 °C | 23.1 °C | 114.55 mm |
| June | 16.1 °C | 28 °C | 106.17 mm |
| July | 17.9 °C | 29.7 °C | 96.27 mm |
| August | 16.7 °C | 28.7 °C | 88.65 mm |
| September | 12.3 °C | 25.9 °C | 92.2 mm |
| October | 5.8 °C | 18.7 °C | 77.47 mm |
| November | -0.3 °C | 10.2 °C | 66.55 mm |
| December | -5.7 °C | 3.2 °C | 53.59 mm |
| Annual | 5 °C | 16.5 °C | 963.68 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 5b : -26.1°C to -23.3°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |