Ventura, CA - December 28: Men watch from a balcony in Faria Beach as huge waves crash on the shore Thursday, Dec. 28, 2023 in Ventura, CA. (Brian van der Brug / Los Angeles Times via Getty Images)
CNN  — 

Offshore storms shoved waves toward communities along the California coast, bringing flooding and road closures, as well as fright to nearly 20 people who were briefly swept away along a Ventura beach on Thursday. Eight people were taken to the hospital, officials said.

The swells will not be a one-day thing: Some areas of the California coast will see towering waves – some up to 30 feet – through the weekend. The waves will usher high water and rip currents. Coastal flood alerts and high-surf alerts stretch from the US-Mexico border to north of the Bay Area.

Waves, coupled with high tides, sent torrents of seawater into Santa Cruz along the central coast.

The Santa Cruz County Sheriff’s Office issued an evacuation warning for some areas. The evacuation warning covered an unincorporated area of the county near Seacliff State Beach and Rio Del Mar, according to a post on the department’s Facebook page.

California Highway Patrol Santa Cruz warned of coastal flooding at the Rio Del Mar Esplanade in a post on X and urged people to avoid the area.

“Rio Del Mar Esplanade is currently flooded. Please avoid the area and do not attempt to drive across flooded areas. Road closures are in effect, so please do not drive around them. Drive with caution and prioritize safety,” it wrote.

Five campers were evacuated along the San Luis Obispo coast Thursday, officials detailed in a social media post.

The spectacular waves drew surfers and onlookers, who gawked at nature’s power.

Just northwest of Los Angeles, 15 to 20 onlookers were briefly swept away after a large wave overtook a beach barrier in a Ventura neighborhood hit by high surf, police Cmdr. Ryan Weeks told CNN.

The onlookers were washed down the street about 30 to 50 yards, Weeks said.

The county fire department posted a video of the rogue wave and the ensuing chaos on X, noting the beaches are currently closed in the county. “Because of this wave eight people were transported to local hospitals,” the agency said.

Streets in the area were closed as a precaution, as was a main access point to the Ventura Pier to encourage people to stay away.

Two men walk through ocean debris in the Rio Del Mar neighborhood of Aptos, Thursday, Dec. 28, 2023. (AP Photo/Nic Coury)

“We’re trying to keep people off the beach to keep them from getting hit by rogue waves,” Weeks said.

Aerial video from CNN affiliate KABC showed the aftermath, as residents in the area tried to clean up the foamy, sandy mess.

The flooding comes as the Southern California coast was being impacted by large swells, the National Weather Service in Los Angeles said in a social media post.

One swell reached about 20 feet at Ventura Pier, the agency added.

“Dangerous surf, life-threatening rip currents, and coastal flooding are expected at the beaches this week. Impacts are expected to become most extreme on Thursday,” weather service posted.

The most significant impacts are expected along the central and Ventura County coasts, along with Hermosa, Manhattan and Palos Verdes beaches, according to the agency.

Fifteen to 20-foot waves are expected in the central coast, bringing potentially damaging coastal flooding.

“Beach conditions becoming extremely dangerous Thursday morning continuing through the weekend,” the National Weather Service in Los Angeles said in its forecast.

Officials recommend beachgoers stay out of the water due to dangerous surf conditions and potentially life-threatening rip currents. Beach erosion also is possible.

“Prepare for significant sea water flooding, especially in low-lying areas (including beaches/harbors) & at high tide,” the weather service said.

Storm debris in the Rio Del Mar neighborhood of Aptos, Thursday, Dec. 28, 2023. (AP Photo/Nic Coury)

In Ocean Beach, near San Diego, the curious and surfers thronged to the beach to take it all in, according to CNN affiliate KGTV.

Not everyone who brought a board got into the roiling surf.

“My friend asked me if I wanted to come check it out, and once I saw it, I knew it was too large and in charge for me,” Gerry Giuliano told the affiliate. “I mean, it’s hitting the pier and that’s a warning sign that it’s pretty big, closing out and breaking pretty quickly, too.”

Northern California is expected to have its own share of problems.

The Bay Area is under a coastal flood warning until 6 p.m. Thursday, with significant coastal flooding expected through the evening hours before conditions begin to improve.

A high-surf warning is in effect in the Bay Area until 3 a.m. Friday.

“Dangerously large breaking waves of 28 to 33 ft with up to 40 ft possible at favored locations,” the weather service said. The agency said San Francisco, Monterey Bay, Point Reyes and Big Sur are among the affected areas.

The Bay Area National Weather Service office said a coastal flood advisory is in effect through 2 p.m. Friday for the combination of high surf and potential storm surge. The advisory stretches from west of Cloverdale south to Big Sur.

An evacuation order was issued for a portion of Marin County near San Francisco but it was later lifted.

A deadly storm slammed the California coast in January 2023.

CNN’s Phil Gast contributed to this report.