Ransom, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 4.9 °C (low) to 15.8 °C (high). Annual precipitation averages 964.9 Millimeters. Ransom is located in USDA Plant Hardiness Zone 5b. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -8.9 °C | -0.3 °C | 51.05 mm |
| February | -7.1 °C | 2.2 °C | 46.23 mm |
| March | -1.7 °C | 9.2 °C | 63.75 mm |
| April | 4.1 °C | 16.3 °C | 91.69 mm |
| May | 10.7 °C | 22.5 °C | 116.59 mm |
| June | 16 °C | 27.4 °C | 114.81 mm |
| July | 17.8 °C | 28.9 °C | 102.36 mm |
| August | 16.7 °C | 28 °C | 95.25 mm |
| September | 12.1 °C | 25.2 °C | 85.85 mm |
| October | 5.7 °C | 18.1 °C | 78.23 mm |
| November | -0.5 °C | 9.6 °C | 66.29 mm |
| December | -5.9 °C | 2.6 °C | 52.83 mm |
| Annual | 4.9 °C | 15.8 °C | 964.93 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| 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 |