Mount Sterling, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 42.1 °F (low) to 62.1 °F (high). Annual precipitation averages 39 Inches. 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 | 17.3 °F | 34.3 °F | 1.92 in. |
| February | 21.0 °F | 39.3 °F | 1.97 in. |
| March | 30.3 °F | 50.9 °F | 2.51 in. |
| April | 41.1 °F | 63.0 °F | 3.98 in. |
| May | 52.7 °F | 72.8 °F | 5.11 in. |
| June | 61.9 °F | 81.6 °F | 4.64 in. |
| July | 65.4 °F | 85.2 °F | 3.67 in. |
| August | 63.2 °F | 83.9 °F | 3.56 in. |
| September | 54.2 °F | 78.0 °F | 3.53 in. |
| October | 43.0 °F | 65.6 °F | 3.24 in. |
| November | 32.2 °F | 51.7 °F | 2.73 in. |
| December | 22.7 °F | 39.2 °F | 2.1 in. |
| Annual | 42.1 °F | 62.1 °F | 38.96 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 |