A potentially historic El Niño is strengthening in the Pacific. For Los Angeles County, preparing for it means thinking beyond rainfall totals – to burn scars, hillsides, canyon roads, freeways, homes and the vehicles millions of people depend upon every day.
Southern California is heading toward winter with an unusual climate signal developing thousands of miles away.
El Niño continues to strengthen across the tropical Pacific, and the National Oceanic and Atmospheric Administration says there is a greater than 90 percent chance that the developing 2026-27 event will become very strong during the fall and winter.
NOAA currently estimates a 75 percent chance that the October-through-December period could reach a level exceeding previous El Niño events in the modern record dating to 1950.
Those numbers deserve attention. They do not mean Los Angeles County is guaranteed a winter of catastrophic rain. El Niño changes the probability of certain weather patterns. It does not tell us in advance whether a particular atmospheric river will strike Los Angeles, how much rain will fall over Altadena, whether Malibu will experience destructive surf, or whether a canyon road will flood on a particular afternoon.
That distinction is important. We don’t need to predict disaster to prepare for conditions we already know can occur in Los Angeles County.
The First Question Is Not “How Much Rain?” It Is “Where Will the Water Go?”
Los Angeles County is an unusual place to manage water. Mountains rise abruptly above heavily populated neighborhoods. Canyons funnel runoff toward developed areas. Natural streams have been replaced or supplemented by concrete channels. Hillsides contain homes, roads, retaining systems and utilities. Large portions of the county have been paved, reducing the amount of water that can naturally soak into the ground.
When rainfall becomes intense, water can move rapidly from the mountains through neighborhoods and into a complex system of streets, channels, storm drains and flood-control infrastructure. Los Angeles County emergency-management guidance warns that flash flooding can develop rapidly and sometimes without visible rain where the flooding occurs. Moving water can carry rocks, mud and debris and can sweep away people and vehicles.
That makes one measurement particularly important during storms: rainfall intensity.
Several inches spread over a long period may create very different consequences from a short burst of extremely heavy rain over one watershed. For residents in hillside and canyon communities – and especially below recent burn scars – the difference can be critical.
Altadena: The Eaton Fire Changed the Watershed
The Eaton Fire did more than destroy homes and vegetation. It changed how portions of the San Gabriel Mountain watershed above Altadena respond to rain.
Wildfire removes vegetation, damages root systems and can alter surface soils. Rain that once infiltrated or moved gradually through vegetation may instead run rapidly downhill. Water can gather sediment, rocks, branches and other material as it moves. That can create flash flooding and debris flows.
The danger is not theoretical. The U.S. Geological Survey documented a debris flow in Rubio Canyon within the Eaton Fire burn area after intense rainfall in February 2025. The resulting flow deposited material ranging from mud to boulder-sized sediment and damaged vegetation within the channel.
USGS subsequently produced a formal post-fire debris-flow hazard assessment for the Eaton Fire. These assessments examine where debris flows are most likely to begin, how large they could become and what rainfall conditions may trigger them.
For Altadena residents, that means a storm should not be judged solely by what is happening directly outside the window. Rain falling higher in the watershed can create consequences downstream. A neighborhood may experience relatively modest rainfall while dangerous runoff is being generated on the burned slopes above it.
Pacific Palisades and Malibu Face a Different Combination of Risks
The Palisades Fire created another large post-fire watershed, but the geography is different. Here, steep Santa Monica Mountains terrain descends toward developed neighborhoods, canyon roads and the Pacific Ocean.
USGS has produced a post-fire debris-flow hazard assessment for the Palisades Fire that identifies watersheds with varying modeled debris-flow likelihood under intense rainfall scenarios.
USGS research on post-fire debris-flow runout notes that flows originating in steep burned watersheds can move rapidly downstream and sometimes travel beyond the burn perimeter into developed areas, threatening homes, roads and infrastructure.
For Pacific Palisades and Malibu, rain can generate runoff and debris from burned hillsides; canyon roads can become vulnerable to mud, rocks and localized flooding; and Pacific Coast Highway can experience rainfall runoff while coastal storms produce high surf, erosion and difficult driving conditions.
In August 2026, the City of Malibu warned about coastal erosion affecting PCH and the potential for winter rain and high surf to worsen vulnerable locations. PCH is more than a scenic highway: it is transportation infrastructure, an evacuation route, an emergency-response corridor and an essential connection among coastal communities.
Burn Scars Change the Rules
There is one principle everyone living near the Eaton or Palisades burn areas should understand: It takes less rain to create dangerous runoff after a wildfire than it did before the fire.
USGS post-fire debris-flow guidance explains that wildfire can substantially change the hydrologic response of a watershed, allowing even relatively modest storms to trigger dangerous flash floods and debris flows in steep burned areas.
The National Weather Service uses a general rule of thumb that roughly one-half inch of rain in less than an hour can sometimes be sufficient to produce flash flooding in a burn area, although actual thresholds vary considerably according to burn severity, slope, soil conditions and rainfall intensity. More important than memorizing a number is understanding the principle: burned terrain responds faster.
When officials issue an evacuation order related to a burn scar, the safest time to leave is before the flow develops.
What About Bel Air, the Hollywood Hills and Mount Washington?
Recent burn scars are not the only concern. Los Angeles contains thousands of homes built on or beneath steep terrain that did not burn in 2025. Communities such as Bel Air, the Hollywood Hills, Mount Washington, Laurel Canyon, Beachwood Canyon and other hillside neighborhoods have a different set of vulnerabilities.
The issue here is often not post-fire debris flow. It is the interaction among steep slopes, intense rainfall, drainage systems, retaining structures, saturated soils and heavily developed terrain. Los Angeles Emergency Management describes the city as a landscape of mountains, canyons, ravines and basins where heavy weather can quickly produce flooding and where landslides can develop on hillsides.
As hillsides absorb water over successive storms, soil can weaken. Retaining walls can experience additional pressure. Existing cracks can widen. Trees can become unstable. Slopes that appeared stable during dry weather may begin to move.
The City recommends watching for warning signs such as newly tilting fences, retaining walls, utility poles or trees; widening cracks in pavement or soil; newly broken utility lines; unusual pools of groundwater; and mud accumulating at the base of a slope. See City of Los Angeles rainstorm guidance for additional information.
Canyon Roads Require Special Respect
Los Angeles residents frequently use canyon roads as alternatives to the freeway system. During intense rain, they may become some of the least predictable roads in the region. Water can cross the pavement. Rocks can fall from slopes. Mud can enter travel lanes. Trees or branches can fall. Drainage systems can become blocked. And in narrow canyons there may be few places to turn around.
During the February 2024 storms, Los Angeles Fire Department reported significant storm impacts including mudslides and debris flows affecting hillsides and roadways.
During major storms, the fastest-looking alternate route on a navigation application may not be the safest route. If a canyon road is closed, respect the closure. Do not drive around barricades.
Then There Is the Freeway System
For most Los Angeles County residents, El Niño’s most frequent impact may not occur at home. It may happen during the commute.
Heavy rain adds several hazards at once: visibility decreases, stopping distances increase, water reduces tire traction, vehicles can hydroplane, storm drains can become temporarily overwhelmed, standing water may collect in low areas, and mud, rocks or vegetation can enter freeway lanes near hillsides.
Even a relatively localized closure can redirect large volumes of traffic onto other freeways and surface streets. The result can become a regional transportation problem even when the actual flooding is highly localized.
California Highway Patrol rain-driving guidance advises drivers to slow down on rain-slicked roads, increase following distance and avoid sudden braking or sharp turns.
During significant storms, allow more time, consider delaying nonessential travel and check conditions before leaving. Caltrans QuickMap provides current information on traffic, CHP incidents, lane closures, highway conditions and full closures.
The Most Dangerous Decision May Be Driving Into Water
Southern Californians are not accustomed to frequently flooded roadways. Water hides the road beneath it. You may not know whether the pavement is intact, whether a storm drain cover has moved, or how deep the water is. Moving water can exert considerably more force than it appears to from inside a vehicle.
Los Angeles County flood guidance warns residents not to enter floodwater. The City’s wet-weather guidance is equally direct: never attempt to drive or walk through a flooded roadway or flowing stream.
IF YOU CANNOT CLEARLY SEE THE ROADWAY, TURN AROUND.
Prepare the House Before the Forecast Turns Red
Storm preparation works best before a major storm appears on a weather application. Walk around your property. Look up. Look down. Look uphill. And look downhill. The objective is to understand how water will interact with the property before thousands of gallons of it begin arriving.
• Clear roof gutters and downspouts.
• Remove leaves, vegetation and debris from drainage paths.
• Make sure water leaving a downspout is not being directed toward the foundation.
• Secure outdoor furniture, trash containers and other items that could enter the street and block storm drains.
• Look at large trees and damaged limbs.
• If your property is on or below a significant slope and you have concerns about stability, consider evaluation by an appropriately qualified professional before winter storms arrive.
Los Angeles Emergency Management wet-weather guidance recommends addressing overgrown trees, clogged gutters and hillside erosion before the rainy season and having tools, tarps and sandbags available.
For City of Los Angeles residents, LAFD provides free ready-to-fill sandbags at neighborhood fire stations, with sand available at selected locations when seasonal conditions warrant. Sandbags can help redirect ordinary runoff. They cannot make a home safe from a major debris flow.
People Rebuilding After the Fires Have Additional Work to Do
For residents rebuilding in Altadena, Pacific Palisades and other fire-affected communities, rain preparedness deserves particular attention. Construction sites and cleared lots may contain exposed soil. Temporary drainage systems need to function correctly. Materials must be secured. Erosion control needs to remain intact. Drainage routes should not be blocked by construction materials, debris containers or vehicles.
LA County burn-area preparation guidance has advised residents to clear drainage paths, use properly placed sandbags where appropriate and keep vehicles and trash containers off streets so stormwater can move freely.
Your Vehicle Needs an El Niño Checkup Too
Preparing the house while ignoring the car misses half the problem in Los Angeles. A reliable vehicle may become essential during an evacuation, power outage or major transportation disruption.
- Tires: Check tread depth and inflation.
- Visibility: Replace worn wipers; check headlights, brake lights and washer fluid.
- Reliability: Check brakes and battery; keep fuel or EV charge adequate.
- Emergency Kit: Carry water, flashlight, first aid, charger/power bank, rain protection and sturdy shoes.
Los Angeles Emergency Management recommends keeping a vehicle at least half fueled during wet weather in case evacuation becomes necessary. CHP’s roadside emergency-kit guidance recommends basic supplies including drinking water, a flashlight, first-aid supplies, jumper cables, a blanket, tools, a tire-pressure gauge and food.
Your Car Is Not a Boat – and Sometimes It Should Stay Parked
One of the most effective vehicle-preparation strategies costs nothing: do not drive when conditions make travel unnecessary or unsafe. If a major storm is expected to produce intense rain during a particular period, consider whether a trip can happen before or after it. Working remotely, delaying an appointment or changing plans may sometimes eliminate considerably more risk than any equipment placed in the vehicle.
City storm-safety guidance recommends limiting non-essential travel during significant storms.
Prepare for Power Outages Too
Heavy rain rarely arrives alone. Strong winds may accompany storm systems. Trees can fall. Branches can contact electrical equipment. Vehicles may strike utility infrastructure. Water intrusion can affect local systems.
Keep phones charged. Maintain portable battery packs. Know how essential medical devices will operate without utility power. Have flashlights available. Know how to manually open a garage door if necessary. Keep medications and other essentials accessible. And never approach a downed power line. Los Angeles storm-safety guidance advises treating every downed line as energized and dangerous.
Know Who Will Warn You
Information becomes especially important because storm impacts can be intensely local. One neighborhood may be relatively unaffected while another a few miles away is experiencing a flash-flood warning.
City of Los Angeles residents should be registered for NotifyLA and ensure Wireless Emergency Alerts are enabled on their phones. Residents should also monitor National Weather Service Los Angeles/Oxnard information and official city or county emergency information.
For traffic, use Caltrans QuickMap and official road-closure information rather than assuming a navigation application knows that a road has just flooded. For burn-scar communities, monitor the Los Angeles County mud and debris-flow forecast whenever significant rain is expected. Ready LA County rain guidance provides additional preparedness information.
Three Things Los Angeles County Residents Should Remember
- BURN SCARS REACT DIFFERENTLY TO RAIN. Altadena, Pacific Palisades and areas downstream from recent fires can experience rapid runoff, flash flooding and debris flows during rainfall that might have created much less concern before the fires.
- HILLSIDES AND CANYONS DO NOT HAVE TO BE BURNED TO BECOME DANGEROUS. Bel Air, the Hollywood Hills, Mount Washington and other steep neighborhoods can experience drainage problems, falling rocks, saturated slopes, landslides and localized flooding during prolonged or intense rain.
- LOS ANGELES IS A TRANSPORTATION SYSTEM AS MUCH AS A COLLECTION OF NEIGHBORHOODS. Flood one underpass, close one canyon road or block several freeway lanes and the consequences may quickly spread through the transportation network.
El Niño Preparation Has Value Even if the Forecast Underperforms
We may not get an extraordinary winter. A very strong El Niño does not guarantee extraordinary Southern California rainfall. That does not make preparation wasted effort.
Cleaning gutters protects a house during an ordinary storm. Inspecting a slope may identify a problem before it becomes catastrophic. Replacing worn tires reduces risk whenever it rains. Preparing a GO bag helps during wildfire, earthquake, flood or another evacuation. Maintaining a charged battery pack helps during any power outage. Understanding alternate routes helps during a fire as much as during a storm. Registering for emergency alerts helps regardless of the hazard.
Preparedness does not require the worst-case scenario to occur in order to have value.
One More Connection: Rain Today Can Influence Wildfire Tomorrow
For wildfire-prone Los Angeles County, El Niño has another consequence worth remembering. Significant winter rain may temporarily reduce wildfire potential. It can also stimulate vegetation growth. Green hillsides in February and March can look reassuring, but grasses and other fine fuels eventually cure and dry.
That does not mean El Niño causes wildfire. It means wildfire preparedness remains a year-round process. A wet winter can provide homeowners and communities with an opportunity to inspect homes, improve defensible space, address home-hardening vulnerabilities, organize neighborhoods and prepare before the next period of critical fire weather.
Do Not Prepare for a Headline. Prepare for Los Angeles.
El Niño will generate plenty of headlines during the months ahead. Some will focus on whether it becomes the strongest on record. Others will ask whether Los Angeles will experience another 1997-98-style winter. Those questions are interesting. They are not the questions that make a household safer.
The useful questions are much closer to home: Where will water go when it reaches my property? Do I live below a slope or burned watershed? Could my normal evacuation route become flooded or blocked? Are my gutters and drains clear? Are my tires ready for heavy rain? Do I have enough fuel or charge to leave if necessary? Do I know an alternate way home? Am I receiving emergency alerts? Would I leave promptly if officials told me to evacuate?
The strength of El Niño will be determined by the Pacific Ocean.
How prepared Los Angeles County is for the consequences will be determined here at home.
