Hurricane Paul rapidly strengthened into a major Category 3 storm in the Pacific Ocean off Mexico on Monday, prompting a hurricane warning for a swath of Baja California's western coast.

The U.S. National Hurricane Center in Miami said Paul's maximum sustained winds had ratcheted up to 195 km/h as of 5 p.m. ET Monday. Paul was centered about 670 kilometres southwest of the tip of the Baja peninsula and moving north-northeast at 20 km/h.

Forecasters said Paul was expected to approach the western coast of the southern Baja peninsula by late Tuesday and be near or over the central Baja peninsula on Wednesday. The hurricane was expected to begin weakening Tuesday, the hurricane center said.

Paul expected to bypass Los Cabos

Paul is on track to bypass the heavily populated tourist areas in Los Cabos, at the tip of the peninsula, and the capital, La Paz, on the eastern Gulf of California.

But the storm could hit land before sweeping along the coast near Puerto San Carlos on the Pacific, a sparsely populated area of fishing villages. The outer cone was forecast to pass over the tourist town of Meluge, farther north on the gulf.

State civil protection authorities say they are monitoring the storm for possible evacuations and have sent advance teams help maintain water and electricity during the storm.

Mexico's government, meanwhile, changed a tropical storm warning for the peninsula's sparsely populated western coast from Santa Fe north to Puerto San Andresito to a hurricane warning, according to the centre.

It said Mexico also has issued a tropical storm warning on Baja's western flank from north of Puerto San Andresito to Punta Abrejojos and also from Agua Blanca to south of San Fe. A tropical storm watch is in effect for some other coastal areas in the storm's projected path.

Rafael reaches hurricane strength

In the Atlantic, meanwhile, Rafael reached hurricane strength late Monday in the Atlantic Ocean south of Bermuda.

The hurricane centre said Rafael's top sustained winds had risen to near 120 km/h, making it the ninth hurricane of the Atlantic season.

Rafael is centered about 905 kilometres south of Bermuda. It is moving north at 17 km/h and forecast to pass near or to the east of Bermuda by late Tuesday.