May in Waukesha averages a daily high of 19.7°C with nights around 8°C. Expect roughly 12.7 wet days totalling 107.5mm. Generally workable, with some weather to plan around.
Across the year, the best time to visit Waukesha is June–September.
Based on WAUKESHA WWTP, WI US (2.2km), 1995–2024. 19 years of May data.