Mount Olive, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 6.7 °C (low) to 17.6 °C (high). Annual precipitation averages 1077.7 Millimeters. Mount Olive is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around Apr. 1 - Apr. 10 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -6.3 °C | 2.3 °C | 65.28 mm |
| February | -4.5 °C | 5.3 °C | 57.66 mm |
| March | 0.5 °C | 11.3 °C | 78.99 mm |
| April | 6.2 °C | 18 °C | 122.17 mm |
| May | 12.3 °C | 23.4 °C | 128.27 mm |
| June | 17.3 °C | 28.3 °C | 110.24 mm |
| July | 19.1 °C | 30 °C | 103.38 mm |
| August | 17.8 °C | 29.6 °C | 87.38 mm |
| September | 13.2 °C | 26.3 °C | 85.85 mm |
| October | 6.8 °C | 19.7 °C | 81.28 mm |
| November | 1.4 °C | 11.6 °C | 89.92 mm |
| December | -3.6 °C | 5 °C | 67.31 mm |
| Annual | 6.7 °C | 17.6 °C | 1077.73 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| Average Days With Frost | 75-100 Days |
| Plant Hardiness Zone | Zone 6b : -20.6°C to -17.8°C |
| Plant Hardiness Zone - 2012 | Zone 6a : -23.3°C to -20.6°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |