Grayville, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 46 °F (low) to 66.6 °F (high). Annual precipitation averages 46.7 Inches. 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 | 24.0 °F | 40.3 °F | 3.5 in. |
| February | 26.7 °F | 45.5 °F | 2.88 in. |
| March | 35.0 °F | 55.4 °F | 4.14 in. |
| April | 45.4 °F | 67.5 °F | 5.02 in. |
| May | 56.1 °F | 77.1 °F | 5.11 in. |
| June | 64.7 °F | 85.6 °F | 4.55 in. |
| July | 67.6 °F | 88.3 °F | 4.17 in. |
| August | 65.5 °F | 87.3 °F | 3.25 in. |
| September | 57.6 °F | 82.0 °F | 3.28 in. |
| October | 46.0 °F | 70.2 °F | 3.43 in. |
| November | 35.7 °F | 55.8 °F | 3.86 in. |
| December | 27.8 °F | 44.6 °F | 3.5 in. |
| Annual | 46 °F | 66.6 °F | 46.69 in. |
| 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 : 0°F to 5°F |
| Plant Hardiness Zone - 2012 | Zone 6b : -5°F to 0°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |