Mendon, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 6 °C (low) to 17 °C (high). Annual precipitation averages 1005.9 Millimeters. Mendon 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. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -7.9 °C | 1.3 °C | 45.47 mm |
| February | -5.9 °C | 4.1 °C | 50.04 mm |
| March | -0.5 °C | 10.7 °C | 64.77 mm |
| April | 5.6 °C | 17.4 °C | 102.62 mm |
| May | 11.8 °C | 23 °C | 130.3 mm |
| June | 17.1 °C | 28.1 °C | 121.67 mm |
| July | 19 °C | 30.2 °C | 102.11 mm |
| August | 17.7 °C | 29.3 °C | 98.04 mm |
| September | 12.9 °C | 25.8 °C | 90.17 mm |
| October | 6.6 °C | 18.8 °C | 82.3 mm |
| November | 0.5 °C | 10.9 °C | 67.56 mm |
| December | -4.9 °C | 3.9 °C | 50.8 mm |
| Annual | 6 °C | 17 °C | 1005.85 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| 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 |