Detroit, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 42.9 °F (low) to 63.4 °F (high). Annual precipitation averages 39.5 Inches. Detroit is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 18.7 °F | 35.6 °F | 2.06 in. |
| February | 22.1 °F | 40.7 °F | 1.96 in. |
| March | 31.3 °F | 52.0 °F | 2.79 in. |
| April | 41.9 °F | 64.5 °F | 4.1 in. |
| May | 53.3 °F | 74.1 °F | 4.7 in. |
| June | 62.6 °F | 82.7 °F | 4.79 in. |
| July | 65.8 °F | 86.2 °F | 4.2 in. |
| August | 63.6 °F | 85.2 °F | 3.41 in. |
| September | 55.0 °F | 79.3 °F | 3.52 in. |
| October | 43.6 °F | 66.8 °F | 2.92 in. |
| November | 33.2 °F | 52.7 °F | 2.9 in. |
| December | 23.9 °F | 40.4 °F | 2.15 in. |
| Annual | 42.9 °F | 63.4 °F | 39.5 in. |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 6a : -10°F to -5°F |
| Plant Hardiness Zone - 2012 | Zone 6a : -10°F to -5°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |