Donnellson, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 5.5 °C (low) to 16.7 °C (high). Annual precipitation averages 994.2 Millimeters. Donnellson is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -8.9 °C | 0.6 °C | 38.86 mm |
| February | -6.9 °C | 3.2 °C | 47.75 mm |
| March | -1.2 °C | 10.2 °C | 64.26 mm |
| April | 4.9 °C | 17.4 °C | 95.25 mm |
| May | 11.5 °C | 23.1 °C | 129.79 mm |
| June | 16.8 °C | 28.3 °C | 126.24 mm |
| July | 18.9 °C | 30.3 °C | 107.19 mm |
| August | 17.7 °C | 29.4 °C | 97.54 mm |
| September | 12.9 °C | 25.8 °C | 97.03 mm |
| October | 6.4 °C | 18.6 °C | 78.23 mm |
| November | 0 °C | 10.3 °C | 62.74 mm |
| December | -5.6 °C | 3.3 °C | 49.28 mm |
| Annual | 5.5 °C | 16.7 °C | 994.16 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 6a : -23.3°C to -20.6°C |
| Plant Hardiness Zone - 2012 | Zone 5b : -26.1°C to -23.3°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |