Glendale Heights, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 4.4 °C (low) to 15.2 °C (high). Annual precipitation averages 994.9 Millimeters. Glendale Heights 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 | -9.3 °C | -0.6 °C | 53.34 mm |
| February | -7.8 °C | 1.6 °C | 52.58 mm |
| March | -2.6 °C | 8.1 °C | 58.17 mm |
| April | 3.1 °C | 15.2 °C | 97.28 mm |
| May | 9.2 °C | 21.4 °C | 123.44 mm |
| June | 14.7 °C | 26.9 °C | 115.32 mm |
| July | 17.5 °C | 29.2 °C | 93.98 mm |
| August | 16.7 °C | 28.1 °C | 105.41 mm |
| September | 12.2 °C | 24.3 °C | 85.85 mm |
| October | 5.6 °C | 16.9 °C | 87.38 mm |
| November | -0.6 °C | 8.9 °C | 65.28 mm |
| December | -6.1 °C | 2.3 °C | 56.9 mm |
| Annual | 4.4 °C | 15.2 °C | 994.93 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 | Abnormally Dry |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |