La Sierra Heights, La Sierra Hills, and Norco Hills are informal names for the northernmost section of the range known as the Temescal Mountains, located in northwestern Riverside County, California. The section begins on the south bank of the Santa Ana River and extends southward between the valleys occupied by the City of Riverside to the east and the Cities of Norco and Corona to the west. A gap or connects these valleys and separates this range from Arlington Mountain and the balance of the range to the south.