Powerful debris flows triggered by the season’s strongest atmospheric river have swept vehicles off a southern California highway, sending one car tumbling into the ocean, while roads became overwhelmed with mud and sludge.

As California navigates its rainy season, strong storms are commonplace during this period. However, this wave of destructive weather follows closely on the heels of recent wildfires that ravaged communities around Los Angeles, significantly amplifying the consequences.

These events underscore the ongoing risks associated with year-round fire hazards. The climate crisis has heightened the chances of extreme weather events occurring simultaneously, with risks set to escalate as global temperatures rise.

Although the intense rainfall began to diminish by Thursday evening, Friday saw persistent threats of rock and mudslides on burned hillsides. Such hazardous slides can occur even after the rain has subsided, particularly in areas scarred by wildfires where vegetation that safeguards the soil has been lost.

One firefighter from the Los Angeles fire department was inside the vehicle when it plunged into the ocean near Malibu, managing to escape with only minor injuries, according to department spokesperson Erik Scott’s update on X.

In Pacific Palisades on Thursday, an intersection was engulfed in at least 3 feet (approximately 1 meter) of mud, causing some drivers to attempt navigating through the muck, while police assisted in clearing a stranded vehicle. Bulldozers were deployed to clear the roads, a scene reminiscent of weeks prior when abandoned cars were moved by crews after wildfire evacuees were caught in traffic.

In north Altadena, a road adjacent to the Eaton fire burn area was also buried beneath several feet of mud, trees, and debris as floodwaters breached concrete barriers designed to mitigate debris flows. The region was mostly uninhabited.

Sierra Madre issued evacuation orders for areas impacted by the Eaton fire, alerting residents via social media that fire, police, and public works personnel would refrain from entering regions experiencing active flows and urging those who stayed behind to shelter in place until the areas were declared safe.

Reports from Azusa indicated that part of a grocery store’s roof collapsed while customers were inside on Thursday evening, but fortunately, all shoppers evacuated safely, according to KABC-TV.

The National Weather Service planned to investigate damage on Friday at a mobile home park in Oxnard, which endured gusts reaching 60mph (96 km/h) on Thursday afternoon, with meteorologist Carol Smith noting they would assess the possibility of a weak tornado.

Further north, snow and ice contributed to significant pileups on highways in Oregon and Washington, resulting in injuries for at least ten individuals as a winter storm swept across the Pacific Northwest.

The storms along the West Coast are part of a series of severe weather events sweeping the US, leaving tens of thousands without power.

Meteorologists are warning that the United States is expecting its 10th and coldest polar vortex outbreak this season. Meteorological activity in the Arctic is pushing colder air typically confined near the North Pole into parts of the US and Europe. This latest cold front is projected to first reach the northern Rockies and northern Plains on Saturday and linger throughout the following week.

As the rainfall intensified on Thursday, the National Weather Service issued warnings for flash floods and severe thunderstorms across a segment of eastern Los Angeles County. The excessive rain triggered rockslides and mudflows in Malibu Canyon, with a significant debris flow covering about 8 inches (20 cm) of roadway in the Hollywood Hills.

On Thursday, southern California recorded rainfall totals of 1 to 2 inches in coastal and valley areas, with totals ranging from 3 to 6 inches across coastal slopes, according to the weather service.

More than 30,000 residents in California experienced power outages, as reported by PowerOutage.us.

Evacuation updates were issued for regions affected by the Palisades fire, one of the most devastating fires in Los Angeles history. The blaze not only destroyed vegetation that stabilizes the soil but also contributed loose debris such as ash, dirt, and rocks to the environment.

Prior to the storm, officials proactively distributed sandbags, deployed rescue swimmers, and advised residents to prepare go-bags. Sandbags and temporary barriers were set up throughout Altadena, where the Eaton fire ravaged numerous homes.

Despite the recent downpours, substantial parts of Southern California still grapple with extreme to severe drought conditions, as indicated by the US Drought Monitor. Climate scientist Daniel Swain from UCLA expressed that while the region desperately needed rain, this particular storm could lead to excessive amounts in a short period.

In Altadena, Mehran Daoudian remained vigilant, covering a hole in his roof with a tarp where flames had breached last month. He expressed his gratitude for the city workers who had organized the placement of sandbags and barriers in his neighborhood.

“I didn’t leave my cars on the street because they might get swept away by the mudslide,” he mentioned.

Near the Airport fire burn scar in Orange County, Trabuco Canyon Road was overwhelmed with mud and debris, as reported by Orange County public works on social media.

In the San Francisco Bay area, reports of power outages, minor landslides, and flooded streets surfaced. Authorities urged residents in Felton Grove, a small community on the central coast, to evacuate as the San Lorenzo River threatened to overflow its banks.

Further east in Nevada, measurable rainfall was recorded in Las Vegas, bringing an end to a 214-day dry streak.

Additionally, in northern Utah, rain and snow combined to create hazardous conditions on mountain roads leading to ski resorts. The state’s department of transportation issued road safety alerts, warning of a mix of heavy snow and rain lasting through Friday.

First responders conducted thorough checks on every vehicle involved in a pileup Thursday, approximately 25 miles (40 km) east of Portland, Oregon, as Multnomah County officials reported. Although initially stated to involve over 100 cars, state transportation officials later revised the figure to 20 to 30 vehicles. Oregon state police confirmed that four individuals were taken to hospitals with minor injuries.

The incident occurred amidst near-whiteout conditions in the westbound lanes of Interstate 84, where an SUV caught fire, although its occupants escaped unscathed.

Multnomah County officials extended a state of emergency through at least Friday, with eight shelters opened for those displaced. Reports indicated that 489 individuals sought refuge in the shelters on Wednesday night.

Wind chill factors in Portland could plummet to 10°F (-12°C), according to weather service forecasts.

In southern Washington, injuries were reported among six individuals involved in a 22-vehicle pileup on Interstate 5 near the Cowlitz River, noted state patrol spokesperson Will Finn. In total, incidents on Thursday led to 95 crashes across five counties in southwestern Washington.