Winfield, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 41.1 °F (low) to 60.9 °F (high). Annual precipitation averages 38 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 | 14.9 °F | 31.4 °F | 1.41 in. |
| February | 18.6 °F | 36.1 °F | 1.71 in. |
| March | 29.0 °F | 49.0 °F | 2.42 in. |
| April | 40.1 °F | 62.2 °F | 3.74 in. |
| May | 51.9 °F | 72.7 °F | 5.12 in. |
| June | 61.8 °F | 81.9 °F | 4.93 in. |
| July | 65.2 °F | 85.3 °F | 4.1 in. |
| August | 62.9 °F | 83.6 °F | 4.07 in. |
| September | 54.1 °F | 77.5 °F | 3.55 in. |
| October | 42.5 °F | 64.7 °F | 2.88 in. |
| November | 31.0 °F | 49.4 °F | 2.27 in. |
| December | 20.8 °F | 36.7 °F | 1.77 in. |
| Annual | 41.1 °F | 60.9 °F | 37.97 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 | Abnormally Dry |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |