California battles 'life-threatening' storms as floods, high surf and avalanches threaten state

Stormy conditions are expected to persist across California, with authorities warning that the risks of flooding, high surf and avalanches remain.

Waves near the San Francisco Bay Area were expected to reach up to 25 feet (7.6 metres), while flood risks remained in parts of Southern California and avalanche conditions threatened the Lake Tahoe region. The storms were blamed for at least two deaths earlier in the week as they hit the area during the busiest travel weeks of the year.

A falling tree killed a San Diego man on Christmas Eve, while farther north, a Sacramento sheriff's deputy died in what appeared to be a weather-related crash. The US National Weather Service had said "life-threatening atmospheric river conditions" would continue throughout Christmas Day.

Atmospheric rivers are long, narrow regions in the atmosphere - like rivers in the sky - that carry water vapour in the atmosphere from tropical regions. When making landfall, water vapour is released in the form of rain or snow.

Atmospheric rivers form worldwide but are particularly impactful along the US West Coast, where they account for roughly 30% to 50% of yearly rainfall. The National Weather Service said the system brought the wettest Christmas season to downtown Los Angeles in 54 years.

'A crazy Christmas' Residents in the mountain town of Wrightwood, about 80 miles (130 kilometres) northeast of Los Angeles, were told to be ready to evacuate due to the threat of mudslides. On Christmas Day, the streets in the town were covered with rocks, debris, and heavy mud.

After the power went out, a gas station and a coffee shop running on generators served as meeting places for residents and visitors. "It's really a crazy Christmas," said Jill Jenkins, who was spending the holiday with her 13-year-old grandson.

The family nearly evacuated the day before after water washed away part of their backyard, but they chose to stay and celebrate the holiday. Davey Schneider hiked about a mile and a half (1.6 kilometres) from his home in Wrightwood on Wednesday, wading through rain and shin-deep floodwaters to rescue cats from his grandfather's house.

"I wanted to help them out because I wasn't confident that they were going to live," Schneider said. "Fortunately, they all lived.

They're all okay - just a little bit scared." Arlene Corte said roads in the town turned into rivers, but her house was not damaged. "It could be a whole lot worse," she said.

"We're here talking." Read more from Sky News:Cold weather health alert stays in place for Boxing DayUkraine hits major Russian oil refinery with British missiles San Bernardino County Fire spokesman Shawn Millerick said that with additional rain expected, over 150 firefighters were deployed in the area. "We're ready," he said.

"It's all hands on deck at this point." State of emergency Governor Gavin Newsom has declared a state of emergency in six California counties to enable state assistance. Areas along the coast, including Malibu, were under a flood watch until Friday afternoon, and wind and flood advisories were issued for much of the Sacramento Valley and the San Francisco Bay Area.

Southern California usually receives 0.5 to 1 inch (1.3 to 2.5 cm) of rain at this time of year, but many areas could see 4 to 8 inches (10 to 20 cm) this week, with even higher amounts in the mountains. Additional wind and heavy snowfall were forecast for the Sierra Nevada, where strong gusts caused "near white-out conditions" and made travel through mountain passes dangerous.

The California National Guard has been put on standby to assist first responders..