December in Waukesha averages a daily high of 0.4°C with nights around -8.2°C. Expect roughly 9.3 wet days totalling 47.6mm. A hard month to visit for comfort alone.
Across the year, the best time to visit Waukesha is June–September.
Based on WAUKESHA WWTP, WI US (2.2km), 1995–2024. 20 years of December data.