Alleman, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 3.8 °C (low) to 15.1 °C (high). Annual precipitation averages 921.8 Millimeters. Alleman 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 | -11.6 °C | -1.8 °C | 24.13 mm |
| February | -9.3 °C | 0.8 °C | 29.72 mm |
| March | -3 °C | 8 °C | 52.83 mm |
| April | 3.3 °C | 15.9 °C | 96.52 mm |
| May | 10 °C | 21.7 °C | 128.27 mm |
| June | 15.8 °C | 27.1 °C | 135.89 mm |
| July | 17.8 °C | 29.1 °C | 109.22 mm |
| August | 16.4 °C | 28 °C | 108.2 mm |
| September | 11.6 °C | 24.7 °C | 87.88 mm |
| October | 4.6 °C | 17.3 °C | 66.55 mm |
| November | -2.2 °C | 8.7 °C | 46.99 mm |
| December | -8.2 °C | 1.2 °C | 35.56 mm |
| Annual | 3.8 °C | 15.1 °C | 921.76 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 |