Rankin, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 5.2 °C (low) to 16.4 °C (high). Annual precipitation averages 996.5 Millimeters. Rankin 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. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -8.3 °C | 0.4 °C | 56.39 mm |
| February | -6.6 °C | 3.1 °C | 49.02 mm |
| March | -1.4 °C | 9.6 °C | 68.07 mm |
| April | 4.3 °C | 17.1 °C | 100.08 mm |
| May | 10.9 °C | 23.2 °C | 113.54 mm |
| June | 16.1 °C | 27.9 °C | 119.13 mm |
| July | 17.7 °C | 29.3 °C | 109.73 mm |
| August | 16.4 °C | 28.4 °C | 87.63 mm |
| September | 12.1 °C | 25.9 °C | 77.47 mm |
| October | 5.8 °C | 18.8 °C | 84.07 mm |
| November | 0 °C | 10.3 °C | 73.41 mm |
| December | -5.2 °C | 3.2 °C | 57.91 mm |
| Annual | 5.2 °C | 16.4 °C | 996.45 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 6a : -23.3°C to -20.6°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 |