Glenwood, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 5.3 °C (low) to 15.3 °C (high). Annual precipitation averages 1020.8 Millimeters. Glenwood 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. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -8.2 °C | 0 °C | 56.64 mm |
| February | -6.7 °C | 2.1 °C | 54.86 mm |
| March | -1.6 °C | 8.2 °C | 60.45 mm |
| April | 4.1 °C | 15.2 °C | 99.57 mm |
| May | 10.2 °C | 21.1 °C | 112.78 mm |
| June | 15.7 °C | 26.6 °C | 119.89 mm |
| July | 18.3 °C | 28.8 °C | 110.49 mm |
| August | 17.3 °C | 27.8 °C | 105.16 mm |
| September | 13.1 °C | 24.4 °C | 83.06 mm |
| October | 6.4 °C | 17.3 °C | 88.9 mm |
| November | 0.5 °C | 9.6 °C | 70.36 mm |
| December | -5.1 °C | 2.9 °C | 58.67 mm |
| Annual | 5.3 °C | 15.3 °C | 1020.83 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| 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 5b : -26.1°C to -23.3°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |