Residents of a southern California mountain community near the Eaton fire burn scar dug out of roads submerged in sludge on Friday after the strongest storm of the year swept through the area, unleashing debris flows and muddy messes in several neighborhoods recently torched by wildfires.

Water, debris and boulders rushed down the mountain in the city of Sierra Madre on Thursday night, trapping at least one car in the mud and damaging several home garages with mud and debris. Bulldozers on Friday were cleaning up the mud-covered streets in the city of 10,000 people.

“It happened very quickly but it was very loud and you could even hear the ground or feel the ground shaking,” Bull Duvall, who has lived in Sierra Madre for 28 years, said of the debris flows.

Sierra Madre officials issued evacuation orders for areas affected by the Eaton fire, warning that fire, police and public works personnel would not enter areas experiencing active mud and debris flows and anyone who remained in a home under evacuation orders would need to shelter in place until areas are deemed safe for city personnel to enter.

Residents of the city also had to evacuate during the Eaton fire, which destroyed 15 homes in the community.

California is in the midst of its rainy season and strong storms are not necessarily unusual for this time of year. But the damaging weather timed so closely after the deadly wildfires that left communities across Los Angeles in ruins last month has increased the impacts.

It’s a foreboding sign of the risks posed when fire dangers lurk throughout the year. The climate crisis has increased the likelihood of compounding extremes and the risks will continue to rise as the world warms.

While the heavy rains from the storm hitting the region began to ease on Thursday night, the risk of rock and mudslides on wildfire-scarred hillsides continued on Friday since dangerous slides can strike even after rain stops, particularly in scorched areas where vegetation that helps keep soil anchored has burned away.

One member of the Los Angeles fire department was in the vehicle when it went into the water in Malibu and was able to exit with minor injuries, a department spokesperson, Erik Scott, said on the social platform X.

In Pacific Palisades on Friday, some residents washed their mud-covered driveways and bulldozers worked to clear mud-coated roads not far from where, just weeks ago, officials moved abandoned cars after people fleeing last month’s wildfires got stuck in traffic and fled on foot.

In north Altadena, a road near the Eaton fire burn scar was also covered in several feet of mud, vegetation and trees as a flood of water overcame concrete blocks put in place to prevent such debris flows. The area was mostly deserted.

In neighboring Sierra Madre, the city issued evacuation orders for areas affected by the Eaton fire, warning in a social media post that fire, police and public works personnel would not enter areas experiencing active mud and debris flows and anyone who remained in a home under evacuation orders would need to shelter in place until areas are deemed safe for city personnel to enter.

Azusa police said the roof of a grocery store partially collapsed while shoppers were inside the store on Thursday evening, but everyone got out safely, KABC-TV reported.

The weather service was expected to survey damage on Friday at a mobile home park in Oxnard that was hit by 60mph (96km/h) wind gusts on Thursday afternoon, the Los Angeles Times reported. They would determine whether there was a weak tornado at the park, the meteorologist Carol Smith said.

The west coast storms are just the latest in a week of bad weather across the US that cut power to tens of thousands.

As the downpour intensified on Thursday, the National Weather Service issued flash flood and severe thunderstorm warnings for a swath of eastern Los Angeles county. The rain caused a rockslide and pushed mud on to the road in Malibu Canyon, and a large debris flow left about 8in (20cm) of mud across a road in the Hollywood Hills.

Southern California reported 1 to 3in of rain in coastal areas and valleys and 3 to 6in across the coastal slopes on Thursday, according to the weather service.

More than 30,000 people in California were without electricity, according to PowerOutage.us.

Evacuation orders and warnings were issued in areas where hillsides were scarred by the Palisades fire, the most destructive in LA history. In addition to burning the vegetation that keeps soil in place, the fires also added loose debris to the landscape, including ash, soil and rocks.

Before the storm, officials distributed sandbags, positioned rescue swimmers and told residents to have go-bags ready. Sandbags and temporary concrete barriers were in place across Altadena, where the Eaton fire destroyed thousands of homes.

Despite recent storms, much of southern California remains in extreme or severe drought, according to the US Drought Monitor. Daniel Swain, a climate scientist at the University of California, Los Angeles, said that while the area was desperate for rain, this storm might bring too much too quickly.

In Altadena, Mehran Daoudian prepared by laying tarp over a hole in his home’s roof where fire burned through it last month. Daoudian said he was grateful that city workers arranged sandbags and concrete barriers in his neighborhood over the past few weeks.

“I did not leave the cars on the street because with the mudslide, [they] might go down,” he said.

Near the burn scar for the Airport fire in Orange county, Trabuco Canyon Road was overtaken by mud and debris, Orange county public works posted on social media.

In the San Francisco Bay area, there were blackouts, small landslides and inundated roadways. Authorities urged people to evacuate Felton Grove, a small community along the central coast, as the San Lorenzo River threatened to top its banks.

In neighboring Nevada, the weather service said it recorded a measurable amount of rain in Las Vegas, ending a streak of 214 days without precipitation.

And in northern Utah, rain and snow created dangerous conditions on mountain roads leading to ski resorts. The state department of transportation issued a road safety alert warning of a mix of heavy snow and rain through Friday.

First responders searched every vehicle in a pileup Thursday near, about 25 miles (40km) east of Portland, Oregon, the Multnomah county sheriff’s office said. The office initially said more than 100 cars were involved, but the state transportation department later said the number was 20 to 30 vehicles. Oregon state police said four people were taken to hospitals with minor injuries.

The pileup happened during near-whiteout conditions in the westbound lanes of Interstate 84, authorities said. An SUV caught fire, but its occupants escaped.

Multnomah county officials extended a state of emergency through at least Friday and said eight shelters would be open. Officials said 489 people went to the shelters on Wednesday night.

Wind chills could dip to 10F (-12C) in Portland, the weather service said.

In southern Washington, six people were taken to hospitals with injuries in another pileup of 22 vehicles on Interstate 5 near the Cowlitz River, a state patrol spokesperson, Will Finn, said. There were 95 crashes on Thursday in five counties in the state’s south-west.