Rantoul, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 5.3 °C (low) to 16.7 °C (high). Annual precipitation averages 1004.6 Millimeters. Rantoul is located in USDA Plant Hardiness Zone 6a. 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 | -8.2 °C | 0.7 °C | 57.15 mm |
| February | -6.5 °C | 3.2 °C | 50.8 mm |
| March | -1.4 °C | 9.7 °C | 69.09 mm |
| April | 4.4 °C | 17.2 °C | 101.09 mm |
| May | 11.2 °C | 23.5 °C | 112.27 mm |
| June | 16.3 °C | 28.2 °C | 117.35 mm |
| July | 17.8 °C | 29.6 °C | 107.44 mm |
| August | 16.5 °C | 28.8 °C | 88.65 mm |
| September | 12.3 °C | 26.2 °C | 80.52 mm |
| October | 5.8 °C | 18.9 °C | 84.58 mm |
| November | -0.1 °C | 10.4 °C | 76.45 mm |
| December | -5.1 °C | 3.4 °C | 59.18 mm |
| Annual | 5.3 °C | 16.7 °C | 1004.57 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 6a : -23.3°C to -20.6°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 |