Winterhaven (formerly, Karmack) is a census-designated place (CDP) in Imperial County, California. Winterhaven is located 6.5 miles (10 km) east of Pilot Knob, The population was 394 at the 2010 census, down from 529 at the 2000 census. It is part of the 'El Centro, California Metropolitan Statistical Area'. North of Interstate 8 and bordering Yuma, Arizona, the town is partly located in the Fort Yuma Indian Reservation. The Colorado River marks the town's eastern border.