(CNN) — A strong storm is forming in the sea Giant waves Along the California coast, officials issued emergency warnings about flooding and storm surges that could damage docks and boats and threaten visitors.
Ventura officials said about 20 people were swept away and eight others were taken to hospital by a wave that crashed into onlookers behind a barrier on a Southern California beach.
High tides and dangerous currents will continue through the weekend along parts of the California coast. This Friday, coastal flooding and high tide warnings cover much of the West Coast from the US-Mexico border to southern Oregon, the National Weather Service said.
High waves (up to 12 meters) could be seen on telephone poles in San Francisco on Friday morning. Waves of 4 to 6 meters are expected on the central coast.
The National Weather Service said dangerous conditions pose an “exceptional risk” of inundation and damage to structures such as docks and ships.
The spectacular waters have captivated some surfers and onlookers, but weather officials warn that waves and strong currents can pose a danger to bystanders.
“Large waves can cause injuries, sweep people off beaches and rocks, and capsize small boats near shore,” the National Weather Service warned.
At least one fisherman who fell overboard in Oxnard Harbor was unharmed, the Ventura County Fire Department said.
Conditions have already led to some road closures and evacuations in California coastal communities, and five campers on San Luis Obispo Beach had to be rescued.
Some coastal streets in Ventura are closed as a precaution. To discourage visitors, officials also closed the main access point to the Ventura pier, which saw a rise of about 20 feet on Thursday.
In Santa Cruz, central California, the sheriff's office issued an evacuation warning Thursday for some areas, including parts of the Rio Del Mar, where seawater surged along coastal roads and reached some homes, CNN affiliate KION reported. The warnings were lifted that day.
The most severe impacts are expected along the Central Coast and Ventura County, Hermosa, Manhattan and Palos Verdes beaches, the Los Angeles Weather Service said Thursday.
But Northern California will not be left out.
The Gulf region is under a high wind warning on Friday and is expected to gust up to 80 kmph. The Meteorological Department warned on Thursday that waves could reach a height of 8.5 to 10 metres.
Rain is expected throughout the Bay Area and north of it Friday, before showers spread south on Saturday.
Giant waves attract surfers to Mavericks
Despite the safety warnings, waves attract surfers eager to take in the famous waves at Mavericks Beach, about 25 miles south of San Francisco.
Professional surfers and spectators flocked to the beach Thursday for a tournament known for having some of the biggest waves in the world, CNN affiliate KGO reported.
Surfers from Brazil, Tahiti and Hawaii were in the water, local resident Ion told the Banner affiliate. “It's very strong, very big,” he said.
“The waves looked absolutely huge, which is what we expected,” said Miguel Blanco, who traveled from Portugal to surf the waves, telling KGO.
“If it's your turn, you should go,” Blanco said. “When you see a big wave you get a little scared but at the same time you feel like going, you go and enjoy the ride.”
CNN's David Williams contributed to this report.
“Music ninja. Analyst. Typical coffee lover. Travel evangelist. Proud explorer.”