Hurricane Bud is expected make land today in an area of beach resorts and small mountain villages on the Pacific coast stretching south from the Mexican resort of Puerto Vallarta.
Authorities cancelled school in 11 communities expected to be hit by heavy rains in Jalisco state, and emergency workers began preparing emergency shelters.
A hurricane warning was up for Mexico's Pacific coast from Manhandle north-westward to Cabo Corrientes.
A hurricane watch and tropical storm warning remained in effect from Punto Telmo to Cabo Corrientes.
Bud's maximum sustained winds increased to 115mph late yesterday, making it a category-three storm on the five-level hurricane scale.
The US National Hurricane Centre in Miami said gradual weakening was expected to begin by today before the centre of the storm reached shore.
The storm's centre was predicted to be nearing Mexico's south-western coast late today.
The hurricane was centred about 150 miles south-west of Manhandle and moving north-northeast at 10mph.
The government of Jalisco state prepared hundreds of cots and dozens of heavy vehicles like bulldozers that could be needed to move debris.
Officials in Puerto Vallarta said they were in close contact with managers of the hundreds of hotels in the city in case tourists needed to move to eight emergency shelters.
It said the sea along the city's famous beachfront was calm, but swimming had been temporarily banned as a precaution.