Prairie du Rocher, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 7.7 °C (low) to 19.6 °C (high). Annual precipitation averages 1101.6 Millimeters. Prairie du Rocher is located in USDA Plant Hardiness Zone 7a. The growing season typically runs from the last frost around Apr. 1 - Apr. 10 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -4.9 °C | 5.1 °C | 63.5 mm |
| February | -3 °C | 8 °C | 60.71 mm |
| March | 1.5 °C | 13.5 °C | 91.19 mm |
| April | 7.1 °C | 20.1 °C | 123.95 mm |
| May | 13.2 °C | 25.2 °C | 130.81 mm |
| June | 18.2 °C | 30.2 °C | 108.2 mm |
| July | 20.2 °C | 31.8 °C | 105.66 mm |
| August | 18.9 °C | 31.3 °C | 84.33 mm |
| September | 14.1 °C | 27.7 °C | 86.11 mm |
| October | 7.6 °C | 21.3 °C | 81.03 mm |
| November | 1.9 °C | 13.4 °C | 92.2 mm |
| December | -2.8 °C | 7.2 °C | 73.91 mm |
| Annual | 7.7 °C | 19.6 °C | 1101.6 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| Average Days With Frost | 75-100 Days |
| Plant Hardiness Zone | Zone 7a : -17.8°C to -15°C |
| Plant Hardiness Zone - 2012 | Zone 6b : -20.6°C to -17.8°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |