Forecasters are warning of an "exceptionally dangerous" wave event along the California coast that "has not occurred in many years" — and in Ventura on Thursday, beachgoers experienced just how dangerous it can be. Video shows a massive rogue wave slamming into a sea wall along the beach, sweeping up a truck and sending numerous people to the hospital. 

Video of the moment shows a crowd standing in a parking lot near the ocean before quickly scrambling to try to outrun the incoming wave, which was so large that it swept up a truck and several people, carrying them through rushing waters. 

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It happened in Ventura, a coastal city roughly an hour northwest of Los Angeles. Ventura County Fire Department shared the footage, saying the "rogue wave" hit the beach at the end of Seward Avenue during a high surf advisory at high tide. The county has seen such high surf that streets were flooded with debris several blocks inland. 

"Because of this wave eight people were transported to local hospitals," the fire department said, adding that Ventura County beaches and the pier are closed. "For your safety, please avoid the area near the ocean, as it can be quite dangerous." 

The National Weather Service is warning that coastlines from Southern to Central California are at "extreme risk" — the highest of its warning levels — of "dangerous surf, life-threatening rip currents and coastal flooding" through the weekend.

Rio Del Mar Esplanade is currently flooded. Please avoid the area. pic.twitter.com/seZbMIAJcF

— Santa Cruz County (@sccounty) December 28, 2023

"Tremendous wave energy across the coastal waters generating extremely dangerous conditions at the beach will continue through this weekend," the National Weather Service warned. "Powerful cyclones over the northern Pacific waters are sending this long-period swell towards Southern California waters, with reported outer water swell heights of 20-27 feet." 

The highest waves are expected along the central coast, where forecasters say they could reach between 15 and 20 feet through Saturday. Ventura County could see waves between 10 and 15 feet, while Santa Barbara and Los Angeles County could see waves between 7 and 12 feet, with some sets reaching 15 to 20 feet in some locations. 

"This is expected to be an exceptional high-surf and coastal flooding event that has not occurred in many years," the weather service said. "Take caution and heed the direction of local authorities and lifeguards." 

The agency has warned people in these areas to stay out of the water, prepare for "significant" flooding and to avoid rocks and jetties near the water. 

"Be wary of sneaker waves (suddenly much larger waves)," the agency said. "Never turn your back on the ocean." 

Northern California will also see its share of intense waves. 

The National Weather Service's San Francisco office said a coastal flood advisory is in effect through 2 p.m. on Friday, and a high surf warning was in effect until 6 a.m. Waves were predicted to break between 28 and 33 feet. 

"Large waves can sweep across the each without warning, pulling people into the sea from rocks, jetties and beaches," the agency warned. "These large waves can be erratic and unpredictable." 

In:
• Weather Forecast
• Los Angeles
• Oceans
• National Weather Service
• California

Li Cohen

Li Cohen is a social media producer and trending content writer for CBS News.