Grant Park, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 40.7 °F (low) to 60 °F (high). Annual precipitation averages 39.7 Inches. Grant 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. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 16.5 °F | 31.9 °F | 2.25 in. |
| February | 19.3 °F | 36.2 °F | 1.96 in. |
| March | 28.6 °F | 47.4 °F | 2.36 in. |
| April | 38.8 °F | 60.3 °F | 3.69 in. |
| May | 50.0 °F | 71.2 °F | 4.38 in. |
| June | 59.8 °F | 80.6 °F | 4.73 in. |
| July | 63.5 °F | 83.7 °F | 4.58 in. |
| August | 61.6 °F | 82.2 °F | 4.09 in. |
| September | 53.5 °F | 76.7 °F | 3.43 in. |
| October | 42.1 °F | 64.0 °F | 3.41 in. |
| November | 31.9 °F | 49.3 °F | 2.7 in. |
| December | 22.2 °F | 37.0 °F | 2.16 in. |
| Annual | 40.7 °F | 60 °F | 39.74 in. |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 5b : -15°F to -10°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 |