Winterset, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 4 °C (low) to 15.5 °C (high). Annual precipitation averages 894.3 Millimeters. Winterset 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 | -10.9 °C | -0.9 °C | 22.35 mm |
| February | -8.6 °C | 2.1 °C | 30.99 mm |
| March | -2.8 °C | 9 °C | 54.1 mm |
| April | 3.5 °C | 16.2 °C | 92.96 mm |
| May | 10.1 °C | 21.8 °C | 127.76 mm |
| June | 15.7 °C | 26.9 °C | 117.09 mm |
| July | 17.9 °C | 29.1 °C | 112.01 mm |
| August | 16.5 °C | 28.3 °C | 93.73 mm |
| September | 11.6 °C | 24.6 °C | 94.23 mm |
| October | 4.8 °C | 17.8 °C | 68.33 mm |
| November | -1.9 °C | 9.2 °C | 50.04 mm |
| December | -7.9 °C | 1.8 °C | 30.73 mm |
| Annual | 4 °C | 15.5 °C | 894.32 mm |
| 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 : -26.1°C to -23.3°C |
| Plant Hardiness Zone - 2012 | Zone 5a : -28.9°C to -26.1°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |