Mendota, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 4.1 °C (low) to 15.3 °C (high). Annual precipitation averages 960.1 Millimeters. Mendota 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 | -10.1 °C | -1 °C | 44.7 mm |
| February | -8 °C | 1.5 °C | 43.43 mm |
| March | -2.6 °C | 8.4 °C | 59.94 mm |
| April | 3.2 °C | 15.9 °C | 91.44 mm |
| May | 9.7 °C | 22.3 °C | 116.84 mm |
| June | 15.2 °C | 27.2 °C | 122.94 mm |
| July | 17.1 °C | 28.8 °C | 106.17 mm |
| August | 15.8 °C | 27.7 °C | 99.57 mm |
| September | 11.3 °C | 24.7 °C | 88.39 mm |
| October | 4.9 °C | 17.6 °C | 75.69 mm |
| November | -1.1 °C | 9.1 °C | 61.47 mm |
| December | -6.8 °C | 1.9 °C | 49.53 mm |
| Annual | 4.1 °C | 15.3 °C | 960.11 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 5b : -26.1°C to -23.3°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 |