Chadwick, Illinois has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 3.3 °C (low) to 15 °C (high). Annual precipitation averages 984 Millimeters. Chadwick is located in USDA Plant Hardiness Zone 5a. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -11.2 °C | -1.6 °C | 40.89 mm |
| February | -9.1 °C | 0.9 °C | 44.96 mm |
| March | -3.3 °C | 7.8 °C | 59.18 mm |
| April | 2.6 °C | 15.5 °C | 96.27 mm |
| May | 9.1 °C | 21.9 °C | 116.84 mm |
| June | 14.7 °C | 27.1 °C | 132.84 mm |
| July | 16.5 °C | 28.7 °C | 119.63 mm |
| August | 15.2 °C | 27.9 °C | 102.11 mm |
| September | 10.5 °C | 24.4 °C | 92.71 mm |
| October | 4.2 °C | 17.3 °C | 71.63 mm |
| November | -1.9 °C | 8.6 °C | 57.4 mm |
| December | -7.7 °C | 1.4 °C | 49.53 mm |
| Annual | 3.3 °C | 15 °C | 983.99 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 5a : -28.9°C to -26.1°C |
| Plant Hardiness Zone - 2012 | Zone 5a : -28.9°C to -26.1°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |