West Allis, Wisconsin has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 3.8 °C (low) to 14 °C (high). Annual precipitation averages 910.6 Millimeters. West Allis 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 | -10.1 °C | -1.4 °C | 44.45 mm |
| February | -8.4 °C | 0.6 °C | 42.93 mm |
| March | -3.4 °C | 6.4 °C | 50.8 mm |
| April | 2.3 °C | 13 °C | 100.84 mm |
| May | 8.3 °C | 19.6 °C | 102.36 mm |
| June | 13.9 °C | 25.2 °C | 122.94 mm |
| July | 17 °C | 27.9 °C | 91.69 mm |
| August | 16.3 °C | 27.2 °C | 94.49 mm |
| September | 11.7 °C | 23.3 °C | 82.3 mm |
| October | 5.3 °C | 16.2 °C | 71.63 mm |
| November | -0.9 °C | 8.2 °C | 54.36 mm |
| December | -6.6 °C | 1.5 °C | 51.82 mm |
| Annual | 3.8 °C | 14 °C | 910.61 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 |