Ohlman, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 6.6 °C (low) to 17.7 °C (high). Annual precipitation averages 1032.5 Millimeters. Ohlman is located in USDA Plant Hardiness Zone 6b. 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 | -6.6 °C | 2.1 °C | 62.99 mm |
| February | -4.7 °C | 5 °C | 53.85 mm |
| March | 0.3 °C | 11.2 °C | 74.42 mm |
| April | 6.1 °C | 18.4 °C | 111.51 mm |
| May | 12.3 °C | 23.9 °C | 120.14 mm |
| June | 17.2 °C | 28.7 °C | 119.13 mm |
| July | 18.9 °C | 30.4 °C | 97.03 mm |
| August | 17.6 °C | 29.7 °C | 81.03 mm |
| September | 13.3 °C | 26.8 °C | 80.26 mm |
| October | 7.2 °C | 19.9 °C | 84.07 mm |
| November | 1.2 °C | 11.5 °C | 84.58 mm |
| December | -3.6 °C | 4.9 °C | 63.5 mm |
| Annual | 6.6 °C | 17.7 °C | 1032.51 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 100-125 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 |