Hemet is a city in the San Jacinto Valley in Riverside County, California, United States. It covers a total area of 27.8 square miles (72 km2), about half of the valley, which it shares with the neighboring city of San Jacinto. The population was 78,657 at the 2010 census. The founding of Hemet antedates the formation of Riverside County. The formation of Lake Hemet helped the city to grow and stimulated agriculture in the area.