The Brief

A major thunderstorm like the one that produced devastating flash flooding in Texas over the holiday weekend is not likely in most of California, but climate scientists say that if the perfect weather at the right time of year and geography align, serious flooding can still wreak havoc here.

There are several significant differences between the recent deluge in Texas, which has killed more than 100 people, and the type of flooding that happens in California. First, in the Golden State, it’s the cold winter months that bring flooding, often from back-to-back atmospheric river storms. The instability caused by these rainstorms, which douse the region in water, can generate thunderstorms of varying intensity and trigger flooding.

California typically doesn’t experience massive warm summertime storms because of its Mediterranean climate. The disastrous Texas flooding is a reminder that the ferocity of Mother Nature isn’t always predictable. As the climate continues to warm, resulting in wetter storms, Californians living near waterways need to be prepared for more extreme weather events.

When California floods in the winter, there’s always the possibility of a deadly event depending on where a storm makes landfall. For instance, last November, an atmospheric river parked over the North Bay, causing localized flooding, killing two in Santa Rosa.

“The magnitude of the severity of the flooding absolutely could happen in California, and it is the kind of flooding that we are very concerned about,” said Daniel Swain, a UC Agriculture and Natural Resources climate scientist. “But the physical meteorology involved would be very different.”

How weather messaging works

In Texas, the National Weather Service issued multiple warnings, including its highest level of alert for once-in-a-generation flooding, Swain said. However, the timing of some of the alerts — in the middle of the night — and the regularity of the warnings may have caused people to either miss them or not take them seriously.

Jay Lund, professor emeritus of civil and environmental engineering at UC Davis, likened the immediacy of flash floods to earthquakes.

A pedestrian walks by a mobile home that shifted off its foundation at a mobile home park following a reported 6.0 earthquake on Aug. 24, 2014, in Napa, California.

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“They happen right away and with almost no warning,” he said. “You have to have an excellent warning system because if it happens in the middle of the night, most people aren’t going to hear it because they’ll be asleep.”

Like in Kerr County in Texas, most California localities don’t use sirens to alert the public about flooding, “because our flooding kind of builds and we can see what is coming in,” state climatologist Michael Anderson said. However, some do, like the Marin County communities of Fairfax, Ross and San Anselmo, which maintain flood horns or sirensthat they sound when flooding is imminent.

California relies heavily on the weather service for messaging about potential flooding from storms.

When it comes to flooding, the weather service issues watches, warnings and advisories. Flash flood warnings also have three different levels, ranging from the base level to catastrophic. Beyond the alerts, the weather service leans on traditional radio broadcasts, local authorities and news outlets to get the word out.

Garcia said the difference between a warning and an advisory is that a warning suggests “there could be trouble,” but an advisory means “the trouble is coming to you.” He recommends that all Bay Area residents sign up for text emergency alerts at alertthebay.org and pay attention to any “action statements” within the message.

“If the action statement says something like get to high ground immediately, that is a cue to take immediate action,” Garcia said. “Whether it’s moving to higher floors, going to the top of a hill, or moving yourself to higher ground.”

Flooding from thunderstorms is possible in California

What distinguishes localized flash flooding events from those in Texas is the duration of the atmospheric river, its geographic location and the level of wetness in the system. Atmospheric rivers in California can last for days and arrive in a succession train, while thunderstorms last for a few hours at most.

“Texas can get these systems that consist of thunderstorms that don’t move very much over a period of time, producing an enormous amount of rainfall,” said John Monteverdi, emeritus professor of meteorology at San Francisco State University. “That’s different from the kind of flooding that happens when the Russian River floods, maybe once every two or three years.”

A Sebastopol resident encounters fellow paddlers in a canoe as he paddles in the floodwaters surrounding the market district, The Barlow, after the Russian River crested its banks on Feb. 28, 2019, in Sebastopol, California.

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Still, a big flash-flood-producing thunderstorm in California isn’t entirely out of the picture and can occur during the summertime in the Sierra Nevada or the deserts across the southeastern part of the state.

“The kind of thing that happened in Texas could also happen in California,” said Nicholas Pinter, associate director of the UC Davis Center for Watershed Sciences. “Anyone out hiking in confined, rugged topography needs to be aware that we have this risk of flash flooding in California, kind of similar to Texas.”

While the Texas thunderstorm covering a broad geographic area and producing a wall of water is “not typical of California,” the “wettest precipitation events are getting wetter” and in turn elevating flood risk, which is in line with the effects of human-caused climate change on storms in both states, said Noah Diffenbaugh, a climate scientist at Stanford University.

“We know we’re in a climate where the kind of intense precipitation that leads to flooding is more likely overall for a given storm,” he said. “Our infrastructure in many cases was not designed and built for the most intense conditions that are now occurring.”

California has experienced numerous wet years that resulted in flooding, including the Great Flood of 1862 and other extreme events in 1955, 1964, 1986 and 1997, as well as more recent occurrences such as 2017 and 2023.

For a major flood to occur anywhere in California, a specific set of ingredients — geographic location, soil moisture and storm intensity — is required, according to Anderson, the state climatologist. He pointed to the winter of 2023, when nine atmospheric rivers hit the state over 18 days.

“That’s almost one every other day, and that led to substantial flooding across the state,” he said. “So, what we look for is different than what Texas has to look out for.”

Camp Mystic stands next a creek that feeds into the Guadalupe River, Monday, July 7, 2025, in Hunt, Texas, after flash flooding swept through the area.

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Wildfire-scorched areas are also susceptible to flooding during atmospheric rivers or heavy rains that fall during a monsoon.

“Fire creates a hydrophobic layer on the soil that magnifies the impact of flooding because the water cannot infiltrate it,” said Anna Serra-Llobet, a researcher at the Center for Catastrophic Risk Management at UC Berkeley.

Serra-Llobet said she worries about flooding next winter across wildfire burn scars, especially in Southern California and the Sierra Nevada, as those areas will be primed for flash floods full of ash and debris. In the case of the Los Angeles fires, those floodwaters could hit urban areas.

She said there needs to be more public outreach on how to respond during a flood.

“People don’t understand the risk where they live, and I think we need more drills to be more prepared,” she said. “Creating a risk culture could help many communities to be more proactive and effective in acting during a disaster.”

The Trump administration is ratcheting up its fight to get more crude flowing through California and reverse the state’s efforts to move away from fossil fuels.

Its latest salvo is a federal review of California’s coastal management program, which is run largely by a state commission that has had a powerful role for decades in shaping development along the coast. Environmental advocates fear federal officials could use the review to strip the California Coastal Commission of its ability to have a say in projects involving federal agencies that affect the state’s rugged coastal bluffs, pristine beaches and world-class surfing spots.

The administration, citing a need for energy security and job creation, has already announced plans for new offshore oil leases in California as well as Florida, where the federal government has not allowed drilling since 1995 because of concerns about oil spills in the Gulf of Mexico.

Trump officials also helped a Texas firm jump-start an old pipeline system that had been idled since its 2015 rupture caused one of California’s worst oil spills, blackening beaches for 150 miles (240 kilometers) from Santa Barbara to Los Angeles and polluting habitat for endangered whales and sea turtles. Federal officials also recently took a step toward authorizing fracking on an old oil platform 9 miles (14 kilometers) off Ventura County — a move opposed by the state’s coastal commission.

“It’s just part of that overall belief that they have, that they’re going to get rid of renewables and go back to good old-fashioned fossil fuels, and what better place to start than California?” said Deborah A. Sivas, a professor of environmental law at Stanford Law School. “We’re the feds — we’re going to tell the state what to do.”

California has some working offshore rigs, but there has been no new oil leasing in federal waters since the mid-1980s and no new state leasing for even longer. The state barred new offshore oil leases after a catastrophic spill in 1969 spewed between 3.5 million and 4.2 million gallons of crude into the Santa Barbara Channel. The disaster killed thousands of seabirds and helped give rise to the modern environmental movement.

California now uses so much solar and wind energy that nearly half the state’s electricity came from renewable resources in 2024, according to the state’s energy commission. That’s also the source of a fight with the Trump administration. Last week, state officials sued the federal government over its buyback of an offshore wind lease aimed at discouraging the expansion of wind energy in favor of fossil fuels.

California has also tried to wean residents off gas-powered cars — another push opposed by the Trump administration.

California’s coastal commission is the latest target

California’s coastal commission, an independent agency with appointed members, was formed in 1972. It has often been in the spotlight for taking up high-profile projects on the state’s tourism-dependent coast. The panel voted against but later approved a U2 guitarist’s plan for mansions on seaside bluffs, though the building proposal was eventually nixed by a court. It also rejected a proposed desalination plant to create drinking water in Huntington Beach.

The commission also has a say in federal projects along California’s coast, in line with a 1972 federal coastal management law. More than 30 states have similar programs to protect their coastal resources and all are subject to periodic federal evaluation.

Commerce Secretary Howard Lutnick announced the unexpected review of California’s program in May while denouncing the commission’s opposition to an expanded launch schedule for SpaceX’s Falcon 9 rockets from Vandenberg Space Force Base. Commissioners cited concerns that more launches could harm sensitive species and limit public access to the coast.

“Obstructionist policies that delay critical national infrastructure in the name of environmental extremism are unacceptable,” Lutnick said. He said the review will examine how California has addressed federal priorities on spaceport infrastructure, offshore oil production, pipeline maintenance and desalination projects.

Targeting California raises a fight that could reverberate nationwide, experts say. Until now, no state with a coastal program has been stripped of its authority to review federal projects. Many Californians who spoke at an hourslong public hearing in Santa Monica in August said they don’t want their state to be the first.

“This isn’t about performance. This is about power,” said Maureen Ellenberger, a Santa Barbara resident who is upset about the decision to let Houston-based Sable Offshore Corp. resume pumping through the old pipeline. “It’s about whether the Trump administration can strip California’s authority because they don’t like the answers the coastal commission gave to oil companies.”

The National Oceanic and Atmospheric Administration is carrying out the review. It isn’t known when it will be completed.

The commission isn’t new to controversy

In the past, California’s coastal commission has clashed with elected officials from both political parties. Democratic Gov. Gavin Newsom rushed to the commission’s defense this year, but in 2025 suspended its permitting requirements for home rebuilding following the devastating Los Angeles area wildfires.

Trump’s battles with the commission began before his first term when he put up a 70-foot (21-meter) flagpole on his golf club in Rancho Palos Verdes. The commission ultimately allowed for it after a lengthy battle.

Last month, the commission unanimously voted to oppose the plan for fracking on a 45-year-old platform in federal waters off Ventura County after a lengthy public hearing. The federal Bureau of Ocean Energy Management released an environmental analysis for the proposal, which energy company DCOR said would more than triple daily oil output in 16 wells from 1,100 barrels to 4,000 barrels.

“This is just simply one of those cases where the juice isn’t worth the squeeze,” Coastal Commissioner Ray Jackson said during a hearing on DCOR LLC’s plan. “It creates far too many opportunities for something to go wrong. When something does go wrong it is our ocean, beaches, wildlife and coastal economy that pay the price.”

The company said it’s evaluating whether to appeal to the commerce secretary.

Legislation that would improve public access to information about violence, medical emergencies, and other serious incidents in privately operated detention facilities in California is now heading to the governor’s desk.

It would require local agencies to release audio and records of 911 calls and other emergency-service calls originating from the facilities upon request. State Sen. Lena Gonzalez, a Democrat from Long Beach, introduced Senate Bill 423 as state investigations and courts are finding serious gaps in essential medical care within the facilities.

“No private contract or detention center wall should be used to hide dangerous conditions or silence people who have been mistreated inside these facilities,” Gonzalez said in a statement.

The bill was prompted by CalMatters reporting on alleged sexual assaults at the Otay Mesa Detention Center in 2025. CalMatters sought information, including 911 audio records and other reports, about alleged rapes and attempted sexual assaults at the facility through a California Public Records Act request. While a San Diego County sheriff’s spokesperson said the agency was not investigating those cases, he said he was unable to turn over additional records because they were part of “a law enforcement investigation.”

“When journalists and reporters attempted to obtain records about reported incidents at these facilities through the Public Records Act, they faced severe pushback from law enforcement, citing vague investigatory records exemptions, despite there being no active investigation,” said Gonzalez before the state Senate vote on Monday afternoon.

“SB 423 would make disclosure mandatory for calls from private detention facilities unless it would substantially interfere with an active investigation being conducted by the agency receiving the request,” she added.

Gonzalez’s bill would require local agencies to turn over recordings and written records of 911 calls from privately run detention facilities, if a member of the public requests them. It includes an exception if an active investigation is underway and requires redacting the names of affected individuals.

The number of people being held by federal immigration authorities in Immigration and Customs Enforcement facilities in California has nearly doubled since early 2025, data shows. Between September 2025 and March 2026, there were six deaths at two of California’s private detention facilities.

The San Diego County Sheriff’s Office had a memorandum of understanding with CoreCivic, the private prison company that operates Otay Mesa. The agreement gave the detention center warden discretion of how to investigate alleged sexual assaults.

In May, the California Attorney General’s office released a 175-page report detailing how the dramatic surge in detainee populations strained conditions and access to medical care at immigration detention facilities across the state.

The San Diego County Sheriff’s Office told KQED it does not have a position on the bill. The Kern County Sheriff’s Department told the Bay Area news agency that it will continue to comply with California laws, “as we always do.”

A recent bill analysis by legislative staff showed no registered opposition to the bill.

The proposed legislation was co-sponsored by Immigrant Defense Advocates and the First Amendment Coalition. It was first introduced on June 12.

Paloma Esquivel, a former Los Angeles Times reporter who now works at the First Amendment Coalition, said county sheriffs resisted and stonewalled her requests for 911 records when she worked as a journalist.

“We have a very strong interest and even an obligation to understand how these facilities are functioning and what is happening inside these facilities that are being paid for with billions of dollars in taxpayer money,” Esquivel told KQED.

Jackie Gonzalez the co-executive director of the Immigrant Defense Advocates said the bill is an important first step in addressing what’s going on inside.

“By supporting SB 423, California sends a clear message that the walls of private detention facilities cannot hide the truth of what is taking place in these facilities,” said Gonzalez.

This article was originally published on CalMatters and was republished under the Creative Commons Attribution-NonCommercial-NoDerivatives license.

Topline:

Street flooding: Roadway flooding was reported this morning on the westbound 134 Freeway at the 5, near Glendale and Griffith Park.

Coastal Flooding: All weekend, forecasters have warned of dangerous rip currents and an elevated risk of coastal flooding.

Flooding was reported yesterday in Seal Beach and Long Beach.

"We have quite a few reports already of waves up to 10 feet on some beaches — Zuma Beach especially, where we've gotten reports [of] strong rip currents," said Todd Hall, a meteorologist with the National Weather Service.

Advisories and closures:

• An ocean water quality rain advisory has been issued for all L.A. County beaches until Wednesday, Sept. 9 at 2 p.m. That means to avoid ocean water contact for at least 72 hours after the rain.
• A coastal flood advisory and a high surf advisory for L.A. and Ventura county beaches remain in effect until Tuesday, Sept. 8 at 11 p.m.
• The City of Seal Beach is closing two beach parking lots due to flooding concerns.

What's next: Hall said to expect more showers across L.A. County throughout Sunday. On Monday, he said isolated rain is expected, mostly in the mountains.