Clear Lake (Dakota: mdéza; "Clear") is a city in and the county seat of Deuel County, South Dakota, United States. The population was 1,273 at the 2010 census.
The city was named after the local Clear Lake.
Clear Lake is located at 44°45′19″N 96°41′6″W (44.755248, -96.684950).
According to the United States Census Bureau, the city has a total area of 3.25 square miles (8.42 km2), of which, 3.07 square miles (7.95 km2) is land and 0.18 square miles (0.47 km2) is water.
Clear Lake has been assigned the ZIP code 57226 and the FIPS place code 12540.
As of the census of 2010, there were 1,273 people, 552 households, and 338 families living in the city. The population density was 414.7 inhabitants per square mile (160.1/km2). There were 617 housing units at an average density of 201.0 per square mile (77.6/km2). The racial makeup of the city was 97.6% White, 0.4% African American, 0.1% Asian, 0.4% from other races, and 1.5% from two or more races. Hispanic or Latino of any race were 1.0% of the population.
There were 552 households, of which 27.4% had children under the age of 18 living with them, 49.5% were married couples living together, 8.2% had a female householder with no husband present, 3.6% had a male householder with no wife present, and 38.8% were non-families. 35.7% of all households were made up of individuals, and 18.5% had someone living alone who was 65 years of age or older.