Alleman, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 38.8 °F (low) to 59.1 °F (high). Annual precipitation averages 36.3 Inches. 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 | 11.2 °F | 28.8 °F | 0.95 in. |
| February | 15.3 °F | 33.5 °F | 1.17 in. |
| March | 26.6 °F | 46.4 °F | 2.08 in. |
| April | 37.9 °F | 60.6 °F | 3.8 in. |
| May | 50.0 °F | 71.1 °F | 5.05 in. |
| June | 60.4 °F | 80.7 °F | 5.35 in. |
| July | 64.0 °F | 84.4 °F | 4.3 in. |
| August | 61.5 °F | 82.4 °F | 4.26 in. |
| September | 52.8 °F | 76.4 °F | 3.46 in. |
| October | 40.3 °F | 63.1 °F | 2.62 in. |
| November | 28.1 °F | 47.6 °F | 1.85 in. |
| December | 17.2 °F | 34.2 °F | 1.4 in. |
| Annual | 38.8 °F | 59.1 °F | 36.29 in. |
| 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 : -15°F to -10°F |
| Plant Hardiness Zone - 2012 | Zone 5a : -20°F to -15°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |