Fort Worth has a humid subtropical climate (Cfa) according to the Köppen climate classification system and is within USDA hardiness zone 8a. This region features very hot, humid summers and mild to cool winters. The hottest month of the year is July, when the average high temperature is , and overnight low temperatures average , giving an average temperature of . The coldest month of the year is January, when the average high temperature is and low temperatures average . The average temperature in January is . The highest temperature ever recorded in Fort Worth is , on June 26, 1980, during the Great 1980 Heat Wave, and June 27, 1980. The coldest temperature ever recorded in Fort Worth was on February 12, 1899. Because of its position in North Texas, Fort Worth is very susceptible to supercell thunderstorms, which produce large hail and can produce tornadoes.