The former tropical storm is the fifth hurricane of the eastern Pacific season.
Hernan's winds reached almost 75 mph (120 kph) early Friday, the minimal strength for hurricane classification.
Forecasters at the center said the hurricane may strengthen slightly over the next two days before moving over cooler waters and weakening.
The hurricane's center was located about 865 miles (almost 1,400 kilometers) southwest of the southern tip of the Baja California peninsula and was moving west out to sea.
