Vermilion, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 6.1 °C (low) to 17.2 °C (high). Annual precipitation averages 1099.8 Millimeters. Vermilion is located in USDA Plant Hardiness Zone 6a. 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 | -7.1 °C | 1.9 °C | 73.66 mm |
| February | -5.3 °C | 4.7 °C | 63.5 mm |
| March | -0.2 °C | 10.8 °C | 80.77 mm |
| April | 5.6 °C | 17.8 °C | 121.41 mm |
| May | 11.7 °C | 23.4 °C | 114.55 mm |
| June | 16.8 °C | 28.2 °C | 126.49 mm |
| July | 18.2 °C | 29.6 °C | 105.92 mm |
| August | 17.1 °C | 29.1 °C | 78.74 mm |
| September | 12.8 °C | 26.1 °C | 79.25 mm |
| October | 6.4 °C | 19.3 °C | 93.98 mm |
| November | 0.7 °C | 11.3 °C | 89.92 mm |
| December | -4.1 °C | 4.6 °C | 71.63 mm |
| Annual | 6.1 °C | 17.2 °C | 1099.82 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 6a : -23.3°C to -20.6°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 |