Grandwood Park, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 4.1 °C (low) to 14.1 °C (high). Annual precipitation averages 959.9 Millimeters. Grandwood Park 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. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -9.7 °C | -1.3 °C | 50.55 mm |
| February | -8.2 °C | 0.7 °C | 50.8 mm |
| March | -3 °C | 6.6 °C | 57.91 mm |
| April | 2.7 °C | 13.6 °C | 99.57 mm |
| May | 8.7 °C | 19.8 °C | 110.49 mm |
| June | 14.3 °C | 25.3 °C | 114.3 mm |
| July | 17.1 °C | 27.8 °C | 94.23 mm |
| August | 16.4 °C | 26.9 °C | 92.2 mm |
| September | 12.1 °C | 23.2 °C | 90.68 mm |
| October | 5.6 °C | 16.1 °C | 81.53 mm |
| November | -0.6 °C | 8.4 °C | 61.98 mm |
| December | -6.2 °C | 1.7 °C | 55.63 mm |
| Annual | 4.1 °C | 14.1 °C | 959.87 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| 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 |