Duncombe, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 2.9 °C (low) to 14.2 °C (high). Annual precipitation averages 916.4 Millimeters. Duncombe 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 | -12.7 °C | -3.1 °C | 22.86 mm |
| February | -10.6 °C | -0.7 °C | 28.7 mm |
| March | -3.9 °C | 6.7 °C | 52.32 mm |
| April | 2.3 °C | 15.1 °C | 95.5 mm |
| May | 9.3 °C | 21.4 °C | 128.27 mm |
| June | 15.3 °C | 26.9 °C | 139.19 mm |
| July | 17.2 °C | 28.6 °C | 107.44 mm |
| August | 15.6 °C | 27.3 °C | 116.08 mm |
| September | 10.6 °C | 24.1 °C | 82.8 mm |
| October | 3.6 °C | 16.8 °C | 65.79 mm |
| November | -3.2 °C | 7.6 °C | 42.93 mm |
| December | -9.3 °C | -0.1 °C | 34.54 mm |
| Annual | 2.9 °C | 14.2 °C | 916.42 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 | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |