Winfield, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 39.7 °F (low) to 59.4 °F (high). Annual precipitation averages 39.2 Inches. Winfield 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 | 15.0 °F | 30.9 °F | 2.07 in. |
| February | 17.7 °F | 34.8 °F | 2.0 in. |
| March | 27.3 °F | 46.6 °F | 2.35 in. |
| April | 37.6 °F | 59.5 °F | 3.88 in. |
| May | 48.6 °F | 70.8 °F | 4.9 in. |
| June | 58.5 °F | 80.6 °F | 4.5 in. |
| July | 63.2 °F | 84.5 °F | 3.81 in. |
| August | 61.6 °F | 82.4 °F | 4.07 in. |
| September | 53.7 °F | 76.0 °F | 3.33 in. |
| October | 41.6 °F | 62.9 °F | 3.52 in. |
| November | 30.6 °F | 48.2 °F | 2.58 in. |
| December | 20.8 °F | 36.0 °F | 2.23 in. |
| Annual | 39.7 °F | 59.4 °F | 39.24 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 |