Hurricane Willa was upgraded to a "potentially catastrophic" Category 5 storm Monday off Mexico's Pacific coast, where it was expected to produce life-threatening wind and flooding, the US National Hurricane Center said.
The powerful hurricane was on course to slam into Mexico somewhere around the resort town of Mazatlan on Tuesday afternoon or evening, the NHC said in its 1500 GMT advisory.
It now has maximum sustained winds of 260 kilometers (160 miles) per hour, making it a maximum Category 5 hurricane, it said.
"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," it said.
Willa is expected to dump 15 to 30 centimeters (six to 12 inches) of rain on parts of Jalisco, Nayarit and Sinaloa states, with some areas getting up to 45 centimeters (18 inches), it said.
"This rainfall will cause life-threatening flash flooding and landslides," it warned.
Large storm swells off the coast are also "likely to cause life-threatening surf and rip current conditions," it said.
The storm was located about 215 kilometers (135 miles) southwest of Cabo Corrientes, churning north at 11 kilometers (seven miles) per hour.
Mexico's government has put various parts of the coast on alert.
Elsewhere, Tropical Storm Vicente -- with maximum sustained winds of 75 kilometers per hour -- was expected to bring "heavy rainfall and flooding" over Mexico's south and southwest.
Mexico's Pacific coast has already been hit by deadly storms and rains this hurricane season.
In September, at least 15 people were killed when flash floods hit the states of Sinaloa and Michoacan, and last week 11 more died in Oaxaca, including seven children.
Mazatlan, on Mexico's Pacific coast, is bracing for the arrival of Hurricane Willa