Hurricane Willa dropped to a Category 4 storm after briefly reaching Category 5 strength as it moved toward Mexico's Pacific coast with winds of 250 kilometers per hour (155 mph), the U.S. National Hurricane Center said.
Willa is expected to make landfall Tuesday afternoon or evening, as an "extremely dangerous major hurricane," according to the hurricane center.
The storm is expected to strike near Mazatlan, a popular beach resort, with a metropolitan area of around 500,000. The city is home to a large number of American and Canadian expatriates. Several other tourist destinations and fishing villages are along the storm's projected path.
As of Monday, the storm was about 190 kilometers southwest of the Pacific town of Cabo Corrientes.
"Slight weakening is forecast to begin on Tuesday, but Willa is expected to be an extremely dangerous major hurricane when it reaches the coast of Mexico," the NHC said.
The governments of Mexico's Sinaloa and Nayarit states have ordered coastal schools to close and have begun to prepare emergency shelters.
Weather officials warn the storm could bring 15 to 45 centimeters of rain to parts of Sinaloa, Nayarit, and Jalisco states, with landslides possible in mountainous areas. Willa is also expected to produce a dangerous storm surge with "large destructive waves," according to the hurricane center.
Further south, Mexico is facing another storm in the Pacific Ocean. Tropical Storm Vicente is expected to weaken to a tropical depression before it makes landfall along the southwestern coast of Mexico on Tuesday.
As of Monday, the storm was churning about 590 kilometers southeast of Manzanillo. The NHC said it could produce heavy rainfall and flooding.
Some reporting was from The Associated Press.