Forecasters have warned of torrential rains and potential flooding in the United States and Mexico as Hurricane Hilary churns off the Baja California peninsula.

The hurricane is due to hit Mexico over the weekend before weakening and moving to southern California, where it would be the region's first tropical storm in 84 years.

Hilary reached a maximum speed of 215 km/h (130 mph) on Friday as it headed towards land.

"Life-threatening and potentially catastrophic flooding are likely over much of Baja California and Southern California this weekend and early next week," the United States' National Hurricane Center (NHC) said in its advisory on Friday.

Mexico cancels non-essential activities

The Mexican state of Baja California canceled non-essential public activities on Friday, including school classes through Monday.

Authorities in Tijuana began setting up temporary shelters and clearing stormwater trains as the hurricane approached. The hilly city is particularly prone to landslides.

"We are a vulnerable city being on one of the most visited borders in the world and because of our landscape," Mayor Montserrat Caballero Ramirez said.

In the neighboring state of Baja California Sur, authorities postponed a large baseball match and closed ports.

"Without being alarmist, we must all take precautions and stock up on water and basic necessities at home, without resorting to panic buying," the state's governor Víctor Manuel Castro Cosio said.

Southern California on high alert

In the south of the US state of California, some national parks were closed and Major League Baseball games were relocated in anticipation of extreme weather, the likes of which has not been seen in decades.

Several cities distributed sandbags to protect properties against floodwaters.

"Weakening is expected to begin by Saturday, but Hilary will still be a hurricane when it approaches the west coast of the Baja California peninsula Saturday night and Sunday," the Miami-based NHC said.

"Hilary is expected to weaken to a tropical storm by late Sunday before it reaches southern California."

Heavy rains are also expected to batter the neighboring states of Arizona and Nevada.

NHS Deputy Director Jamie Rhome warned of flood risks in major cities including San Diego, Los Angeles, Palm Springs and Las Vegas.

"If you've got weekend plans, it's probably time to start altering those plans," he said.