The first hurricane of the 2010 season had maximum sustained winds of about 75 mph (120 kph) and was expected to gradually strengthen.
A Category 1 hurricane, Celia was centered about 365 miles (590 kilometers) south of Acapulco on Sunday afternoon, the U.S. National Hurricane Center in Miami said.
The storm was moving westward at about 7 mph (11 kph). That course would take Celia into the open Pacific, and forecasters said there was no immediate threat to land.
Dario Rodriguez, a forecaster at Mexico's National Meteorological Service, said Mexico would not be affected by wind or rain from Celia because it was too far out to sea.
Rodriguez said the hurricane could cause some increased waves along the southern Pacific coast in the states of Oaxaca, Guerrero and possibly Michoacan.
Elsewhere, Blas weakened from a tropical storm to tropical depression, with maximum winds of 35 mph (55 kph).
That storm was centered far out to sea - 470 miles (755 kilometers) southwest of the southern tip of Mexico's Baja California peninsula - and was moving west-northwest at about 13 mph (20 kph).
