Mount Sterling, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 5.6 °C (low) to 16.8 °C (high). Annual precipitation averages 989.6 Millimeters. Mount Sterling 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 | -8.2 °C | 1.3 °C | 48.77 mm |
| February | -6.1 °C | 4.1 °C | 50.04 mm |
| March | -0.9 °C | 10.5 °C | 63.75 mm |
| April | 5.1 °C | 17.2 °C | 101.09 mm |
| May | 11.5 °C | 22.7 °C | 129.79 mm |
| June | 16.6 °C | 27.6 °C | 117.86 mm |
| July | 18.6 °C | 29.6 °C | 93.22 mm |
| August | 17.3 °C | 28.8 °C | 90.42 mm |
| September | 12.3 °C | 25.6 °C | 89.66 mm |
| October | 6.1 °C | 18.7 °C | 82.3 mm |
| November | 0.1 °C | 10.9 °C | 69.34 mm |
| December | -5.2 °C | 4 °C | 53.34 mm |
| Annual | 5.6 °C | 16.8 °C | 989.58 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 |