South Wilmington, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 4.7 °C (low) to 15.8 °C (high). Annual precipitation averages 965.4 Millimeters. South Wilmington 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 | -9 °C | -0.2 °C | 52.07 mm |
| February | -7.3 °C | 2.1 °C | 45.72 mm |
| March | -2.1 °C | 8.8 °C | 61.47 mm |
| April | 3.8 °C | 16.1 °C | 92.71 mm |
| May | 10.2 °C | 22.3 °C | 118.36 mm |
| June | 15.7 °C | 27.4 °C | 116.33 mm |
| July | 17.6 °C | 29.1 °C | 104.9 mm |
| August | 16.5 °C | 28.1 °C | 95.5 mm |
| September | 12 °C | 25.2 °C | 84.07 mm |
| October | 5.5 °C | 17.9 °C | 78.23 mm |
| November | -0.3 °C | 9.7 °C | 64.01 mm |
| December | -5.8 °C | 2.7 °C | 52.07 mm |
| Annual | 4.7 °C | 15.8 °C | 965.44 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 |