Millersburg, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 4.7 °C (low) to 15.5 °C (high). Annual precipitation averages 960.1 Millimeters. Millersburg is located in USDA Plant Hardiness Zone 5b. 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 | -9.9 °C | -0.8 °C | 38.1 mm |
| February | -7.9 °C | 1.7 °C | 45.21 mm |
| March | -2.1 °C | 8.9 °C | 62.48 mm |
| April | 4.1 °C | 16.3 °C | 95.76 mm |
| May | 10.7 °C | 22.2 °C | 125.48 mm |
| June | 16.1 °C | 27.3 °C | 119.89 mm |
| July | 18.1 °C | 29.1 °C | 101.6 mm |
| August | 16.8 °C | 27.9 °C | 99.31 mm |
| September | 12.3 °C | 24.6 °C | 92.71 mm |
| October | 5.7 °C | 17.5 °C | 71.88 mm |
| November | -0.8 °C | 9.3 °C | 58.42 mm |
| December | -6.5 °C | 2.2 °C | 49.28 mm |
| Annual | 4.7 °C | 15.5 °C | 960.12 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 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 |