Percy, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 7.8 °C (low) to 19.2 °C (high). Annual precipitation averages 1130.8 Millimeters. Percy is located in USDA Plant Hardiness Zone 7a. 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 | -4.7 °C | 4.8 °C | 71.88 mm |
| February | -2.7 °C | 7.7 °C | 66.55 mm |
| March | 1.8 °C | 13.2 °C | 99.57 mm |
| April | 7.4 °C | 19.7 °C | 128.02 mm |
| May | 13.3 °C | 24.7 °C | 129.54 mm |
| June | 18.2 °C | 29.6 °C | 114.81 mm |
| July | 20.1 °C | 31.2 °C | 99.57 mm |
| August | 18.8 °C | 30.6 °C | 75.44 mm |
| September | 14.2 °C | 27.2 °C | 86.11 mm |
| October | 7.8 °C | 21.1 °C | 82.04 mm |
| November | 2.2 °C | 13.2 °C | 99.31 mm |
| December | -2.4 °C | 7 °C | 77.98 mm |
| Annual | 7.8 °C | 19.2 °C | 1130.82 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| 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 |