Tourists and local residents in a Mexican resort area fled or sought refuge as Hurricane John lashed the Baja California peninsula with towering waves and powerful winds.
The storm appeared to wobble toward the northeast, diverting its full force from the popular holiday spot of San Jose del Cabo at the peninsula's tip late on Friday.
But forecasts showed John crossing the peninsula further to the north later in its path.
Officials feared flash floods and mudslides in the desert region, which has hills and dry riverbeds that are likely to fill with water from John's heavy rains.
John packed winds of at least 175 km an hour, the US National Hurricane Centre said.
At least 21,000 people on the southern Baja peninsula were evacuated to safer locations and 10,000 tourists fled the region.
"This is a very, very dangerous hurricane," said Ignacio Arrenguin of Mexico's National Water Commission.
"This hurricane is much more serious than any hurricane we had in the last 10 years."
At 2.00 pm (2100 GMT), the centre of the storm was located 95 km east of the southern tip of the peninsula, and was moving north-northwest at about 13 km per hour, the US National Hurricane Centre reported.
John, which had been classified as a category three storm earlier, lost a little strength and was downgraded to a strong category two storm by Friday afternoon.
On the US East Coast, tropical depression Ernesto lashed the Mid-Atlantic states with heavy rain, causing flooding in parts of North Carolina and Virginia and leaving up to 400,000 people without electricity in three states, CNN reported.
Four deaths were blamed on the storm, media reports said.