Hanna is an unincorporated community in western Duchesne County, Utah, United States, on the Uintah and Ouray Indian Reservation. It lies along State Route 35 northwest of the city of Duchesne, the county seat of Duchesne County. Its elevation is 6,765 feet. Although Hanna is unincorporated, it has a post office, with the ZIP code of 84031. Hanna was named for its original postmaster, William P. Hanna.This climatic region is typified by large seasonal temperature differences, with warm to hot summers and cold winters. According to the Köppen Climate Classification system, Hanna has a humid continental climate, abbreviated "Dfb" on climate maps.