 The largest is Lake Waconia, Minnesota's 73rd largest lake and the Twin Cities' second largest lake, with an area of 2,996 acres.In recent years, average temperatures in the county seat of Chaska have ranged from a low of in January to a high of in July, although a record low of was recorded in January 1970 and a record high of was recorded in July 1988.Average monthly precipitation ranged from in February to in August.