Clinton, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 41.6 °F (low) to 62.1 °F (high). Annual precipitation averages 40 Inches. Clinton is located in USDA Plant Hardiness Zone 6a. 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 | 17.2 °F | 33.7 °F | 2.34 in. |
| February | 20.4 °F | 38.5 °F | 2.03 in. |
| March | 29.5 °F | 50.1 °F | 2.81 in. |
| April | 40.4 °F | 63.4 °F | 3.99 in. |
| May | 52.1 °F | 73.8 °F | 4.55 in. |
| June | 61.3 °F | 82.6 °F | 4.56 in. |
| July | 64.3 °F | 85.4 °F | 4.21 in. |
| August | 62.1 °F | 83.6 °F | 3.36 in. |
| September | 54.4 °F | 78.8 °F | 3.13 in. |
| October | 42.6 °F | 65.9 °F | 3.48 in. |
| November | 31.7 °F | 51.1 °F | 3.08 in. |
| December | 22.9 °F | 38.6 °F | 2.49 in. |
| Annual | 41.6 °F | 62.1 °F | 40.03 in. |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 6a : -10°F to -5°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 |