(CNN) 鈥� With parts of Los Angeles County still smoldering from wildfires and flaring up earlier this week, expected rainfall this weekend would seem like a welcome relief. But how the rain falls could make the difference between a disaster respite or a disaster repeat.
Los Angeles County faces a high chance of widespread rain this weekend, with light intensities spread across many hours, the National Weather Service said.
While isolated, heavy rainfall of up to 0.5 inches an hour is expected, it will generally be beneficial for the region.
But the ground in LA hasn鈥檛 seen a drop of rain this year. 鈥淚t behaves more like cement; the ground can鈥檛 accept the water, so it all goes to runoff immediately,鈥� said Ariel Cohen, the meteorologist in charge of the National Weather Service office in Los Angeles.
So if the rain falls at a slow, steady pace that can be absorbed by burn-scarred ground, the showers will be helpful.
But brief blasts of rain could cause flash flooding that would loosen soil and debris on charred hillsides, sending it tumbling toward decimated neighborhoods.
鈥淚t could result in fast-moving flows of mud, rock and fire debris that all conglomerate and spread quickly downhill,鈥� Cohen said.
鈥淚t has the potential to be damaging as it does so, taking down other structures. And certainly could be a threat to life and property.鈥�
A will be in place from 4 p.m. Sunday through 4 p.m. Monday for the locations of Los Angeles-area wildfires from the last six months that have left vulnerable burn scars 鈥� the Palisades, Franklin, Eaton, Hughes and Bridge fires.
What little vegetation is left 鈥渋s not enough to hold back the mud when the water comes and that water comes right into the communities that were so devastated by these tragic fires,鈥� Los Angeles County Fire Department Chief Anthony Marrone told CNN鈥檚 Jessica Dean on Saturday.
鈥淲hile damaging debris flows are not the most likely outcome, there is still a lot of uncertainty with this storm,鈥� the National Weather Service said in a post on X. 鈥淭he threat is high enough to prepare for the worst-case scenario.鈥�
Get sandbags before the rain, official warns
Local and state authorities 鈥� stung by criticism they didn鈥檛 do enough to prevent the wildfire destruction 鈥� say they鈥檙e ready for potential consequences of the rainfall.
Los Angeles Mayor Karen Bass issued an to help keep polluted water and mud from entering city storm drains. The city is expediting debris cleanup and installing concrete barriers in burn areas.
Marrone says the fire department is partnering with the sheriff and public works department to prepare. Hydrologists are also looking at remediation plans and officials are communicating with residents who have returned to their homes in evacuation areas.
More than 250,000 sandbags have been placed in flood-prone areas, the said. Crews also dug pits into hillsides called 鈥渄ebris dams鈥� to catch sediment that might break loose during rainfall.
Residents in areas at risk of landslides should get 鈥渟andbags ahead of time鈥� and know how to shut off all utilities at home, Los Angeles County Fire Department .
He said sandbags are available at local fire stations.
鈥淪tay away from areas susceptible to flooding. Do not attempt to enter moving water,鈥� Richardson warned. 鈥淒o not try to rescue someone who is being swept away. Instead, call 911.鈥�
The rain forecast comes on the tail end of another period that prompted nearly 100,000 power customers to have their as a precaution Thursday.
New wildfires flare up
The catastrophic Palisades and Eaton fires, which have killed 28 people and since January 7, have not grown much in size in over a week. But a spate of fresh wildfires has tormented Southern California this week.
鈥淲e鈥檙e on day 19 during our firefight, and we鈥檝e had very little rain since April of 2024, so we need the rain,鈥� Marrone said. 鈥淲e just don鈥檛 need it all at once.鈥�
Two new blazes erupted Thursday afternoon in San Diego County.
The Border 2 Fire prompted an and torched over 6,600 acres as of . The fire is still at but firefighters conducted a controlled burn near the Otay Reservoir overnight to help limit the fire鈥檚 progression to the US-Mexico border.
While the Border 2 Fire area is not densely populated, 鈥淭here is a ,鈥� said the California Department of Forestry and Fire Protection, also known as Cal Fire.
The Gilman Fire, south of La Jolla, also started Thursday and torched 2 acres before it , Cal Fire said.
Back in Los Angeles County, the has incinerated more than 10,400 acres since it erupted near Castaic Lake on Wednesday. Several areas are warnings, and the blaze was 90% as of Saturday evening.
Haunting memories of past landslides
Forecasters don鈥檛 expect the kind of rainfall that led to some of the region鈥檚 most destructive recent land flows. The Santa Barbara County community of Montecito was after a winter storm immediately followed the , a blaze that killed 23 people.
And the unique geography of Southern California leaves some areas in constant danger of land instability.
The coastal city of suffered sudden movement from a last fall, twisting roads and putting multimillion-dollar homes on the brink of destruction.
The city has into 鈥渄ewatering wells,鈥� sucking more than 112 million gallons of destabilizing water out of the ground in a desperate effort to shore up neighborhoods.
A preview of the worst-case scenario following this weekend鈥檚 rainfall could be seen in the Palisades two weeks ago, when an that survived the wildfire was literally split in half by a mudslide 鈥� apparently triggered by runoff from the water used to fight the fire.
鈥淭here are mud and debris flow hazards that are existing even when it鈥檚 not raining,鈥� Los Angeles County Public Works director Mark Pestrella said.
A fire victim who lost her home says she never got an evacuation warning
Raya Reynaga鈥檚 home perished in the deadly Eaton Fire, and the Altadena resident nearly suffered the same fate.
鈥淚 did not get a warning. I did not get anybody knocking on my door,鈥� Reynaga told CNN on Friday. 鈥淚 was the last person on my street. They had to come get me.鈥�
Adding to the chaos: 鈥淭he day before, we had power outages,鈥� Reynaga said. 鈥淭hat day, it was completely dark black. No power. It was just a nightmare.鈥�
Reynaga is among many residents from who say they never got a warning to evacuate during the Eaton Fire, which .
A CNN investigation revealed weaknesses in emergency alert systems .
Los Angeles County officials are now to review the emergency alert system used during the recent Eaton and Palisades fires.
鈥淭his independent assessment will also ensure we are better prepared for future disasters and can act swiftly to protect lives and property,鈥� Los Angeles County Board of Supervisors said this week.
Reynaga had one message for officials about the missing evacuation alerts:
鈥淒o better, because lives have been lost,鈥� she said. 鈥淭his is completely unacceptable.鈥�
Trump鈥檚 threat to withhold aid would 鈥榙evastate and victimize us all over again鈥�
President Donald Trump traveled to California on Friday after visiting western North Carolina, which was devastated by .
California Gov. Gavin Newsom said the White House didn鈥檛 tell him about Trump鈥檚 visit, but said he鈥檚 鈥済lad鈥� the president accepted his invitation.
Trump has threatened to withhold aid to California, saying state officials need to change how they manage water. On Friday, Trump before California could get 鈥渁 lot of help from the US.鈥�
鈥淚 want two things: I want voter ID for the people of California 鈥� and I want the water to be released,鈥� Trump said during his stop in North Carolina.
In a Truth Social post, Trump Los Angeles lacked the water to put out the fires because the governor chose to protect an 鈥渆ssentially worthless fish called a smelt,鈥� which is only found in Northern California.
But whatever ill will there may be between Newsom and Trump, the two greeted each other warmly Friday in Los Angeles, with Trump telling reporters on the tarmac, 鈥淚 appreciate the governor coming out and meeting me.鈥�
鈥淲e鈥檒l be talking a little bit - we want to get it fixed,鈥� Trump said. Newsom thanked him for visiting and said he expects they will 鈥渂e able to work together to get the speedy recovery.鈥�
Reynaga, who said she hasn鈥檛 received any financial aid from her insurance company or the federal government after losing her home, called Trump鈥檚 threat 鈥渢errible.鈥�
鈥淲e need to rebuild. We need funding. We need financing,鈥� Reynaga said. 鈥淪o that would just devastate and victimize us all over again.鈥�
California Attorney General Rob Bonta told that putting conditions on aid to a state suffering from a natural disaster is a 鈥済reat mistake.鈥�
鈥淭he president ran for president to be the president of the United States of America, not just the red states of America,鈥� he said. 鈥淒oesn鈥檛 matter what party preference the state has.鈥�
CNN鈥檚 Taylor Romine, Brandon Miller, Ella Nilsen, Lauren Mascarenhas, Samantha Waldenberg, Jeff Zeleny, Mike Madrigal, Kia Fatahi and Dalia Faheid contributed to this report.
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