Mendon, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 42.8 °F (low) to 62.5 °F (high). Annual precipitation averages 39.6 Inches. 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 | 17.8 °F | 34.4 °F | 1.79 in. |
| February | 21.3 °F | 39.3 °F | 1.97 in. |
| March | 31.1 °F | 51.2 °F | 2.55 in. |
| April | 42.0 °F | 63.4 °F | 4.04 in. |
| May | 53.3 °F | 73.4 °F | 5.13 in. |
| June | 62.7 °F | 82.5 °F | 4.79 in. |
| July | 66.2 °F | 86.3 °F | 4.02 in. |
| August | 63.8 °F | 84.7 °F | 3.86 in. |
| September | 55.3 °F | 78.4 °F | 3.55 in. |
| October | 43.9 °F | 65.9 °F | 3.24 in. |
| November | 32.9 °F | 51.6 °F | 2.66 in. |
| December | 23.2 °F | 39.0 °F | 2.0 in. |
| Annual | 42.8 °F | 62.5 °F | 39.6 in. |
| 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 : -10°F to -5°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 |