Allison, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 2.8 °C (low) to 13.9 °C (high). Annual precipitation averages 908.8 Millimeters. Allison 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 | -12.9 °C | -3.6 °C | 23.88 mm |
| February | -10.7 °C | -1.1 °C | 27.18 mm |
| March | -4.2 °C | 6.2 °C | 45.21 mm |
| April | 2.2 °C | 14.7 °C | 96.52 mm |
| May | 9.2 °C | 21.3 °C | 125.73 mm |
| June | 15.2 °C | 26.7 °C | 145.8 mm |
| July | 16.9 °C | 28.3 °C | 110.74 mm |
| August | 15.4 °C | 27.1 °C | 102.87 mm |
| September | 10.7 °C | 23.8 °C | 86.87 mm |
| October | 3.9 °C | 16.3 °C | 65.53 mm |
| November | -3.1 °C | 7.1 °C | 44.2 mm |
| December | -9.2 °C | -0.4 °C | 34.29 mm |
| Annual | 2.8 °C | 13.9 °C | 908.82 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 |