Mexico's Baja California peninsula is on alert as Hurricane Jimena nears, packing winds of 250km/h (155mph).
The storm is just below the maximum category five strength, according to the US National Hurricane Center.
Jimena is expected to reach the Los Cabos resort area later on Tuesday or early Wednesday, forecasters say.
Residents have been boarding up homes and schools are closed, and emergency officials are urging people to leave the areas most at risk from the storm.
Francisco Cota, the head of the civil protection agency in Los Cabos, said evacuation plans would focus on the most densely-populated areas.
"It will place special emphasis on the more than 20,000 families who live in high-risk areas," he said.
Police, firefighters and navy personnel have been going through slum areas to try to persuade people to leave their flimsy shacks, AP reported.
Residents are gearing up for the most powerful storm so far this year
"For the safety of you and your family, board a vehicle or head to the nearest shelter," firefighter Ricardo Villalobos said through a loudspeaker. But few seemed keen to leave.
Many tourists, meanwhile, have been heading out of the area rather than spend a couple of days in a storm shelter.
In La Paz, the capital of the state of Baja California Sur, residents rushed to stockpile goods as the most powerful hurricane of the year so far approached, AFP news agency reported.
The US National Hurricane Center warned of a "storm surge along with large and dangerous battering waves" which could "produce significant coastal flooding along the Baja California peninsula".
The agency said that although Jimena's strength was likely to fluctuate, it would make landfall as a major hurricane.
The peninsula is largely desert and mountains but also has resorts and fishing villages.
The US issued an alert to American citizens, urging them to reconsider travelling to areas of Mexico and the United States lying in its path.
The Organization for Economic Co-operation and Development (OECD) conference on tax havens had been due to take place in Los Cabos on Tuesday and Wednesday.
It was "transferred to Mexico City because of the threat of severe damage posed by Hurricane Jimena", the OECD said.
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