Mackinaw, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 5.1 °C (low) to 16.7 °C (high). Annual precipitation averages 984.2 Millimeters. Mackinaw 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 | -8.7 °C | 0.6 °C | 56.39 mm |
| February | -6.8 °C | 3.3 °C | 49.53 mm |
| March | -1.4 °C | 10.1 °C | 65.53 mm |
| April | 4.5 °C | 17.3 °C | 96.77 mm |
| May | 10.8 °C | 23.2 °C | 119.38 mm |
| June | 16.2 °C | 28 °C | 108.46 mm |
| July | 17.9 °C | 29.8 °C | 100.84 mm |
| August | 16.7 °C | 28.9 °C | 92.2 mm |
| September | 12.3 °C | 26.3 °C | 83.82 mm |
| October | 5.8 °C | 18.9 °C | 78.99 mm |
| November | -0.3 °C | 10.6 °C | 74.93 mm |
| December | -5.6 °C | 3.5 °C | 57.4 mm |
| Annual | 5.1 °C | 16.7 °C | 984.24 mm |
| 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 : -23.3°C to -20.6°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 |