December in West Allis averages a daily high of 2.3°C with nights around -6.4°C. Expect roughly 12.2 wet days totalling 62.5mm. A hard month to visit for comfort alone.
Across the year, the best time to visit West Allis is August–September.
Based on WEST ALLIS, WI US (2.5km), 1995–2024. 12 years of December data.