Grayville, 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 1185.9 Millimeters. Grayville 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. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -4.4 °C | 4.6 °C | 88.9 mm |
| February | -2.9 °C | 7.5 °C | 73.15 mm |
| March | 1.7 °C | 13 °C | 105.16 mm |
| April | 7.4 °C | 19.7 °C | 127.51 mm |
| May | 13.4 °C | 25.1 °C | 129.79 mm |
| June | 18.2 °C | 29.8 °C | 115.57 mm |
| July | 19.8 °C | 31.3 °C | 105.92 mm |
| August | 18.6 °C | 30.7 °C | 82.55 mm |
| September | 14.2 °C | 27.8 °C | 83.31 mm |
| October | 7.8 °C | 21.2 °C | 87.12 mm |
| November | 2.1 °C | 13.2 °C | 98.04 mm |
| December | -2.3 °C | 7 °C | 88.9 mm |
| Annual | 7.8 °C | 19.2 °C | 1185.92 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| 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 |