Heyworth, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 41.5 °F (low) to 61.9 °F (high). Annual precipitation averages 39.9 Inches. Heyworth 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 | 16.9 °F | 33.2 °F | 2.21 in. |
| February | 20.2 °F | 38.0 °F | 2.01 in. |
| March | 29.4 °F | 49.8 °F | 2.71 in. |
| April | 40.2 °F | 63.1 °F | 3.89 in. |
| May | 51.9 °F | 73.8 °F | 4.32 in. |
| June | 61.3 °F | 82.5 °F | 4.58 in. |
| July | 64.3 °F | 85.6 °F | 4.12 in. |
| August | 62.0 °F | 83.6 °F | 3.93 in. |
| September | 54.3 °F | 78.8 °F | 3.46 in. |
| October | 42.6 °F | 65.7 °F | 3.5 in. |
| November | 31.7 °F | 50.8 °F | 2.8 in. |
| December | 22.6 °F | 38.2 °F | 2.4 in. |
| Annual | 41.5 °F | 61.9 °F | 39.93 in. |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 125-150 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 |