For water based activities, the summer is the time to come to Lake Chelan. Around Memorial Day, you will find people starting to enjoy the lake, with numerous boats on sunny weekends. But the large deep lake is on the cooler side, especially in May. The lake starts to warm up in June, typically hitting 70 degrees at the lower end of the lake by August. The waterpark, Slidewaters, also typically opens on Memorial Day, staying open until September.
While Lake Chelan is a natural lake, there was a dam built in the early 1900's and now the water level of the lake is controlled by the Chelan Public Utility District. The lake level starts lowering in the fall, and starts rising in the spring, with full level by July 4th. The lake level usually doesn't have too much impact unless you are renting a house with a boat lift, in which case it may not be accessible until June.
Additionally, both Twenty-Five Mile Creek State Park and Lake Chelan State Park have swimming areas, however a Discover or day pass is required to access state parks. There are a couple of nearby swimming areas on the Columbia River, including Chelan Falls Park. Click on the link below to view al the swimming spots around Lake Chelan
