Duncan, Nebraska has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 3.8 °C (low) to 16.2 °C (high). Annual precipitation averages 725.2 Millimeters. Duncan 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 | -10.7 °C | 0.4 °C | 16.26 mm |
| February | -8.4 °C | 2.9 °C | 18.29 mm |
| March | -2.8 °C | 9.7 °C | 39.62 mm |
| April | 3.1 °C | 16.5 °C | 72.9 mm |
| May | 9.7 °C | 22.4 °C | 120.14 mm |
| June | 15.8 °C | 28.1 °C | 115.06 mm |
| July | 18.2 °C | 30.2 °C | 82.55 mm |
| August | 16.7 °C | 28.9 °C | 86.36 mm |
| September | 11.5 °C | 25.4 °C | 63.75 mm |
| October | 4.2 °C | 18.1 °C | 55.37 mm |
| November | -3 °C | 9.6 °C | 32 mm |
| December | -8.6 °C | 2.4 °C | 22.86 mm |
| Annual | 3.8 °C | 16.2 °C | 725.16 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 5b : -26.1°C to -23.3°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |