Roscoe, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 3.6 °C (low) to 14.3 °C (high). Annual precipitation averages 962.7 Millimeters. Roscoe 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 | -10.8 °C | -2.1 °C | 41.91 mm |
| February | -9.1 °C | 0.3 °C | 41.66 mm |
| March | -3.3 °C | 7.1 °C | 53.85 mm |
| April | 2.7 °C | 14.3 °C | 92.96 mm |
| May | 9.1 °C | 20.8 °C | 110.74 mm |
| June | 14.7 °C | 26.3 °C | 137.41 mm |
| July | 16.8 °C | 28.3 °C | 96.27 mm |
| August | 15.9 °C | 27.4 °C | 106.68 mm |
| September | 11.2 °C | 23.7 °C | 96.01 mm |
| October | 4.8 °C | 16.5 °C | 74.17 mm |
| November | -1.5 °C | 8 °C | 60.96 mm |
| December | -7.1 °C | 1.1 °C | 50.04 mm |
| Annual | 3.6 °C | 14.3 °C | 962.66 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 |