Chapin, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 42.5 °F (low) to 63.3 °F (high). Annual precipitation averages 39.9 Inches. Chapin 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 | 18.4 °F | 35.2 °F | 2.15 in. |
| February | 21.8 °F | 40.3 °F | 1.94 in. |
| March | 30.9 °F | 51.8 °F | 2.78 in. |
| April | 41.4 °F | 64.5 °F | 4.07 in. |
| May | 52.9 °F | 74.3 °F | 4.81 in. |
| June | 62.2 °F | 83.0 °F | 4.92 in. |
| July | 65.5 °F | 86.1 °F | 4.0 in. |
| August | 63.1 °F | 84.9 °F | 3.49 in. |
| September | 54.6 °F | 79.4 °F | 3.4 in. |
| October | 43.2 °F | 67.0 °F | 3.06 in. |
| November | 32.7 °F | 52.5 °F | 2.97 in. |
| December | 23.6 °F | 40.3 °F | 2.28 in. |
| Annual | 42.5 °F | 63.3 °F | 39.87 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 6a : -10°F to -5°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |