Fayetteville, 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 1117.6 Millimeters. Fayetteville is located in USDA Plant Hardiness Zone 6b. 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 | -5.1 °C | 4.6 °C | 69.09 mm |
| February | -3.3 °C | 7.5 °C | 61.98 mm |
| March | 1.6 °C | 13.2 °C | 88.14 mm |
| April | 7.4 °C | 19.7 °C | 127.76 mm |
| May | 13.3 °C | 24.8 °C | 127 mm |
| June | 18.3 °C | 29.8 °C | 121.92 mm |
| July | 20.4 °C | 31.6 °C | 105.16 mm |
| August | 19.2 °C | 31 °C | 85.34 mm |
| September | 14.4 °C | 27.4 °C | 82.04 mm |
| October | 7.8 °C | 21.1 °C | 77.72 mm |
| November | 1.9 °C | 13.1 °C | 96.52 mm |
| December | -2.8 °C | 6.9 °C | 74.93 mm |
| Annual | 7.8 °C | 19.2 °C | 1117.6 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 6b : -20.6°C to -17.8°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 |