The best time for a trip to Lake Constance is during the summer months when the weather is 68°-75° and perfect for swimming or spending evenings by the lake. Even if you rent a camper van in Constance (Aach) in spring or fall, you can still do a lot. Hike up one of the many mountains around the lake, or spend the day exploring the city. In June, there’s also a great open-air theatre. Go and see the annual play at Münsterplatz and then stroll through the pleasant summer night. Athletic enthusiasts can sign up for the annual Old Town Run on the 3rd Sunday in October. In Bregenz, Austria, you can visit the Bregenz Festival every year in July and August, which has the world’s biggest stage on a lake.