May in Mount Prospect averages a daily high of 20.9°C with nights around 9.6°C. Expect roughly 12 wet days totalling 98.4mm. Comfortable conditions for being outdoors all day.
Across the year, the best time to visit Mount Prospect is May–September.
Based on CHICAGO PALWAUKEE AIRPORT, IL US (6.6km), 1995–2024. 27 years of May data.