Physical Characteristics. Volusia County is on the Atlantic coast, north of the Melbourne-Titusville-Cocoa area, and is bordered by Brevard, Seminole, Lake, Putanam, Marion, and Flagler counties. The county has 1112.81 square miles of land and 151.94 square miles of water for a total of 1264.75 square miles. The average January temperature is 59.3 degrees fahrenheit, and the average August temperature is 81.5 degrees fahrenheit. The average annual rainfall 53.36 inches. History. Volusia was established from a portion of Mosquito County in 1854 and named for a landing called "Volusia" near Lake George on the St. Johns River. The origin of the name is unknown, but may be from a Frenchman or Belgian named "Veluche."