London Mills, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 4.9 °C (low) to 16.5 °C (high). Annual precipitation averages 972.8 Millimeters. London Mills 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 | -9.2 °C | 0.3 °C | 48.26 mm |
| February | -7.2 °C | 2.9 °C | 48.01 mm |
| March | -1.6 °C | 10 °C | 62.74 mm |
| April | 4.2 °C | 17.3 °C | 95 mm |
| May | 10.9 °C | 23.1 °C | 128.02 mm |
| June | 16.3 °C | 28 °C | 118.62 mm |
| July | 17.9 °C | 29.8 °C | 103.89 mm |
| August | 16.6 °C | 28.9 °C | 90.93 mm |
| September | 12.1 °C | 25.7 °C | 93.47 mm |
| October | 5.3 °C | 18.7 °C | 74.42 mm |
| November | -0.7 °C | 10.3 °C | 60.96 mm |
| December | -5.9 °C | 3.3 °C | 48.51 mm |
| Annual | 4.9 °C | 16.5 °C | 972.83 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 125-150 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 |