May in Dubuque averages a daily high of 21.6°C with nights around 10.1°C. Expect roughly 12.8 wet days totalling 114.5mm. Generally workable, with some weather to plan around.
Across the year, the best time to visit Dubuque is August–September.
Based on DUBUQUE LOCK AND DAM 11, IA US (4.6km), 1995–2024. 30 years of May data.