Glen Ellyn, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 4.6 °C (low) to 15.3 °C (high). Annual precipitation averages 1004.6 Millimeters. Glen Ellyn is located in USDA Plant Hardiness Zone 6a. 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 | -9.1 °C | -0.4 °C | 54.36 mm |
| February | -7.7 °C | 1.7 °C | 53.34 mm |
| March | -2.4 °C | 8.2 °C | 58.93 mm |
| April | 3.3 °C | 15.3 °C | 98.81 mm |
| May | 9.4 °C | 21.6 °C | 123.44 mm |
| June | 15.1 °C | 27 °C | 115.82 mm |
| July | 17.8 °C | 29.3 °C | 95.5 mm |
| August | 16.9 °C | 28.2 °C | 106.43 mm |
| September | 12.5 °C | 24.4 °C | 85.6 mm |
| October | 5.7 °C | 17.2 °C | 88.9 mm |
| November | -0.4 °C | 9.1 °C | 65.79 mm |
| December | -5.9 °C | 2.4 °C | 57.66 mm |
| Annual | 4.6 °C | 15.3 °C | 1004.58 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 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 |