Jimena, a dangerous Category 4 storm, could rake southern Baja California by Tuesday evening, forecasters said.
"I think it's going to be a substantial hurricane by the time it approaches," said Richard Pasch, a senior specialist with the National Hurricane Center in Miami.
Economists from around the world were scheduled to attend a conference sponsored by the Paris-based Organization of Economic Cooperation and Development on Tuesday and Wednesday in Los Cabos at the southern tip of the peninsula. It was not clear if the conference will still take place; the organization's office was closed Sunday.
Brenda Munoz, who lost her home when Hurricane Juliette struck Baja in 2001, was taking no chances, stocking up on food this time around.
"I remember when Hurricane Juliette hit with a lot of intensity. It flattened our home, lots of flooding, lots of disaster," Munoz said at the resort town of Cabo San Lucas. "We're already prepared with food and everything so it won't catch us off guard."
But with the weather still mild Sunday, Jim Patterson, a tourist from Big Bear Lake, Calif., could not muster up much concern.
"Are you saying it would be a good idea to stock up on tequila?" he joked at a seaside restaurant. "No fear. I've been through tornados and earthquakes and everything else, but never a hurricane."
At least 10,000 families will be evacuated from potential flood zones, said Francisco Cota, the local director of Civil Protection. He said 60 shelters would be set up.
Farther south, Jimena kicked up surf along the mainland western coast and generated strong winds that bent trees in the resort town of Zihuatanejo, uprooting at least one. Strong waves and wind prevented a couple on a boat from reaching port, forcing them to spend the night at sea, said Zihuatanejo coast guard official Jose Angel Lara.
Early Monday, Jimena had maximum sustained winds near 145 mph (230 kph) and was moving northwest near 8 mph (13 kph).
It was centered about 395 miles (635 kilometers) south-southeast of Cabo San Lucas and 245 miles (395 kilometers) southwest of Cabo Corrientes, a coastal town in the western state of Jalisco.
Authorities in Cabo Corrientes were setting up shelters in case of heavier wind and rain, said Arturo Garcia, an official with Jalisco's Civil Protection agency.
The U.S. hurricane center issued a public advisory for residents in western Mexico and the southern part of the Baja peninsula to keep tabs on Jimena.
Farther out in the Pacific, a weakening Tropical Storm Kevin had top winds of 40 mph (65 kph) and was centered about 895 miles (1,435 kilometers) west-southwest of the Baja peninsula's southern tip.