Stewardson, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 6.5 °C (low) to 17.8 °C (high). Annual precipitation averages 1078.2 Millimeters. Stewardson is located in USDA Plant Hardiness Zone 6b. 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 | -6.5 °C | 2.4 °C | 69.6 mm |
| February | -4.8 °C | 5.1 °C | 58.42 mm |
| March | 0.2 °C | 11.3 °C | 78.49 mm |
| April | 6.1 °C | 18.3 °C | 119.38 mm |
| May | 12.2 °C | 23.9 °C | 120.14 mm |
| June | 17.2 °C | 28.8 °C | 122.68 mm |
| July | 18.8 °C | 30.5 °C | 106.43 mm |
| August | 17.5 °C | 29.8 °C | 76.96 mm |
| September | 13.1 °C | 26.9 °C | 76.96 mm |
| October | 6.9 °C | 20 °C | 88.14 mm |
| November | 1 °C | 11.6 °C | 91.44 mm |
| December | -3.6 °C | 5.1 °C | 69.6 mm |
| Annual | 6.5 °C | 17.8 °C | 1078.24 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 6b : -20.6°C to -17.8°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 |