Westervelt, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 6.3 °C (low) to 17.6 °C (high). Annual precipitation averages 1036.8 Millimeters. Westervelt 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 | -6.8 °C | 2.1 °C | 62.23 mm |
| February | -5.2 °C | 4.9 °C | 52.58 mm |
| March | -0.1 °C | 11 °C | 72.64 mm |
| April | 5.8 °C | 18.1 °C | 114.3 mm |
| May | 12.1 °C | 23.8 °C | 119.63 mm |
| June | 16.9 °C | 28.6 °C | 121.41 mm |
| July | 18.6 °C | 30.3 °C | 98.3 mm |
| August | 17.4 °C | 29.7 °C | 78.49 mm |
| September | 12.9 °C | 26.8 °C | 78.49 mm |
| October | 6.6 °C | 19.9 °C | 86.36 mm |
| November | 0.7 °C | 11.4 °C | 87.63 mm |
| December | -3.8 °C | 4.8 °C | 64.77 mm |
| Annual | 6.3 °C | 17.6 °C | 1036.83 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 |