Hurricane Paul strengthened on Monday into a "major" storm in the Pacific off Mexico's Baja peninsula, where authorities have warned residents to make quick preparations, US forecasters said.

At 2100 GMT, Paul -- now a category three hurricane on the five-level Saffir-Simpson scale -- was about 670 kilometers (415 miles) southwest of the southern tip of Baja California, the US National Hurricane Center said.

The hurricane is packing maximum sustained winds of 195 kilometers per hour (120 mph), but forecasters said they believed it would weaken on Tuesday, when it is expected to approach the west coast of the Baja peninsula.

"Preparations to protect life and property should be rushed to completion" along the coast, the NHC said in its latest bulletin on the storm.

Isolated areas could see up to eight inches (20 centimeters) of rainfall, the center said, adding that the storm could produce "life-threatening flash floods and mudslides" in mountainous areas.

Paul was also expected to generate dangerous ocean swells and rip currents.

Meanwhile, in the Atlantic, Rafael strengthened into a hurricane, packing maximum sustained winds of 120 kilometers an hour and located about 900 kilometers south of Bermuda.

Rafael -- the ninth hurricane of the Atlantic season -- was expected to "pass near or to the east of Bermuda" late Tuesday, the National Hurricane Center said.