Physical Characteristics. Pinellas County is bordered by Tampa Bay, the Gulf of Mexico, and Pasco and Hillsborough counties. The county has 280.18 square miles of land and 70.80 square miles of water for a total of 350.98 square miles. The average January temperature is 62.1 degrees fahrenheit, and the average August temerature is 82.7 degrees fahrenheit. The average annual rainfall is 54.53 inches.
History. Pinellas County was established in 1911 from a portion of Hillsborough County. The name is derived from Spanish "Punto Pinal," meaning "point of pines."
