Glen Ellyn, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 40.3 °F (low) to 59.6 °F (high). Annual precipitation averages 39.6 Inches. 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 | 15.6 °F | 31.2 °F | 2.14 in. |
| February | 18.2 °F | 35.1 °F | 2.1 in. |
| March | 27.7 °F | 46.7 °F | 2.32 in. |
| April | 38.0 °F | 59.5 °F | 3.89 in. |
| May | 49.0 °F | 70.9 °F | 4.86 in. |
| June | 59.1 °F | 80.6 °F | 4.56 in. |
| July | 64.0 °F | 84.7 °F | 3.76 in. |
| August | 62.4 °F | 82.7 °F | 4.19 in. |
| September | 54.5 °F | 76.0 °F | 3.37 in. |
| October | 42.3 °F | 62.9 °F | 3.5 in. |
| November | 31.2 °F | 48.3 °F | 2.59 in. |
| December | 21.4 °F | 36.3 °F | 2.27 in. |
| Annual | 40.3 °F | 59.6 °F | 39.55 in. |
| 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 : -10°F to -5°F |
| Plant Hardiness Zone - 2012 | Zone 5b : -15°F to -10°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |