Coal Valley, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 40.8 °F (low) to 60.1 °F (high). Annual precipitation averages 38.2 Inches. Coal Valley is located in USDA Plant Hardiness Zone 5b. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 14.3 °F | 30.4 °F | 1.58 in. |
| February | 17.9 °F | 34.9 °F | 1.73 in. |
| March | 28.5 °F | 47.9 °F | 2.47 in. |
| April | 39.6 °F | 61.2 °F | 3.67 in. |
| May | 51.5 °F | 72.3 °F | 4.9 in. |
| June | 61.4 °F | 81.5 °F | 4.83 in. |
| July | 65.1 °F | 84.5 °F | 4.24 in. |
| August | 62.9 °F | 82.7 °F | 3.94 in. |
| September | 54.6 °F | 76.8 °F | 3.61 in. |
| October | 42.9 °F | 63.9 °F | 2.89 in. |
| November | 30.9 °F | 48.8 °F | 2.31 in. |
| December | 20.5 °F | 35.9 °F | 2.07 in. |
| Annual | 40.8 °F | 60.1 °F | 38.24 in. |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 5b : -15°F to -10°F |
| Plant Hardiness Zone - 2012 | Zone 5b : -15°F to -10°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |