Sergio, with winds of nearly 75 mph, was located 480 miles south of Manzanillo, Mexico, and was creeping southeastward at 2 mph, the U.S. National Hurricane Center in Miami said.
Sergio was expected to stay over water, parallel to the Mexican coast, over the next five days. A small, compact hurricane, its winds extended only 45 miles out from the center. Tropical storms become hurricanes when wind speeds reach 74 mph.
The Associated Press contributed to this report.