Dozens of people watched the construction of emergency barriers in the Pierpont area of downtown Ventura, where a rogue wave on Thursday hit spectators and vehicles as it overtook the beach and swept through neighborhoods.
"We've had water in the street once before, but never like this," said Caris Cutivan, a 9-year-old resident of the scenic shoreline town about 60 miles (97 kilometers) northwest of Los Angeles.
"What it's taught me is that I want to be on the beach, not on the beach," Cutivan said.
Eight people were taken to hospitals to be treated for injuries following the Pierpont incident, according to Ventura County officials, who closed beaches, piers and harbors until December 31.
Similar waves reached beaches elsewhere on the California coast on Thursday, flooding parking lots, roads and prompting warnings to evacuate low-lying areas.
There was less rough seas on Friday, but the National Weather Service warned that another round of extremely dangerous surf would return on Saturday.
The Los Angeles-area weather office wrote that the powerful cyclone was producing 12 to 17-foot (3.6 to 5 m) waves over North Pacific waters, producing "tremendous wave energy in coastal waters."
At some points in California, waves were predicted to reach 25 feet (7.6 m). Astronomical high tides are raising the risk of significant coastal flooding, forecasters said.
"Overall, this is expected to be an extraordinary high-surf and coastal flooding event that has not occurred in many years," the weather service wrote. “Use caution and pay attention to instructions from local authorities and lifeguards. Never turn your back to the water as there is a possibility of damaging and life-threatening sneaker waves.
In Airport, which was also hit by heavy waves this week, the weather service downgraded the high surf warning to an advisory on Friday. The weather service said large waves of 18 to 22 feet (5.5 to 6.7 m) and strong currents would make swimming dangerous at some north-facing beaches.
AP reporter Jennifer Cinco Kelleher reported from Honolulu.
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