Hemet is a city in the San Jacinto Valley in Riverside County, California, United States. It covers a total area of 27.847 square miles (72 km), about half of the valley, which it shares with the neighboring city of San Jacinto. The population was 78,657 at the 2010 census. Hemet was founded in 1887, predating the formation of Riverside County, and was incorporated on January 20, 1910. The formation of Lake Hemet helped the city grow and prosper, and stimulated agriculture in the area.