Santa Cruz, California - A pier in California collapsed into the ocean and floated away on Monday, weather authorities said, as the region was pounded by a powerful storm.

Lifeguards rescued two people after the structure in Santa Cruz broke free, firefighters said, while a third person managed to get themselves out of trouble.

Videos posted on social media showed part of the pier adrift in the water as waves lashed the coastline.

Santa Cruz resident Joe Merrill, who was working on the pier when it broke apart, told AFP it happened suddenly.

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"About 300 to 500 feet of the wharf collapsed," he said. "The crane, cargo... all of it just collapsed. Two people went in the water, but they were rescued. We had divers, boats, everything."

The National Weather Service (NWS) reposted a video of the aftermath, explaining: "A portion of the Santa Cruz Pier has collapsed, and is floating away.

"Look at the ominous wave action on the horizon. You are risking your life, and those of the people that would need to try and save you by getting in or too close to the water."

The NWS said towering waves were expected in the area over the next day.

"Dangerous and life-threatening beach conditions are forecast with very high surf, rip currents, sneaker waves, and coastal flooding through Tuesday for ALL beaches along the Pacific Coast," a post on X said.

"Very rough seas, breaking waves to 40 feet and extremely dangerous conditions."

The storm hitting California was expected to bring rain to many areas, even the usually-dry far south around Los Angeles, and snow over the mountains.

It was then expected to move inland.

"A series of Pacific storm systems will cross the Northwest US this week bringing gusty winds, periods of heavy rain, and mountain snow," a forecast said. "A few locally severe storms could occur across parts of central and East Texas on Tuesday."