Carroll, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 3.1 °C (low) to 14.8 °C (high). Annual precipitation averages 848.4 Millimeters. Carroll is located in USDA Plant Hardiness Zone 5a. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -12.1 °C | -2.3 °C | 21.34 mm |
| February | -9.8 °C | 0.3 °C | 27.94 mm |
| March | -3.7 °C | 7.8 °C | 49.78 mm |
| April | 2.3 °C | 15.5 °C | 87.38 mm |
| May | 9.4 °C | 21.6 °C | 118.36 mm |
| June | 15.4 °C | 27.3 °C | 128.78 mm |
| July | 17.3 °C | 28.9 °C | 104.9 mm |
| August | 15.8 °C | 27.7 °C | 102.36 mm |
| September | 10.7 °C | 24.6 °C | 75.18 mm |
| October | 3.9 °C | 17.3 °C | 64.52 mm |
| November | -3.1 °C | 8 °C | 36.07 mm |
| December | -8.8 °C | 0.6 °C | 31.75 mm |
| Annual | 3.1 °C | 14.8 °C | 848.36 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 5a : -28.9°C to -26.1°C |
| Plant Hardiness Zone - 2012 | Zone 5a : -28.9°C to -26.1°C |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |