NOAA sees an increasing chance of a historic El Niño this winter. Here’s what that could mean for our national forests, mountain communities, and backcountry.El Niño is getting stronger, and Southern California could be in for an unusually wet winter.
On October 8, the National Oceanic and Atmospheric Administration (NOAA) reported that ocean temperatures in the central and eastern equatorial Pacific continued to climb through September. The Niño-3.4 region reached 3.8°F above average, while portions of the eastern Pacific exceeded 7.2°F above normal.
NOAA now gives the developing El Niño an 83% chance of reaching historic strength during October through December 2026, potentially exceeding every El Niño event recorded since 1950. There’s also a greater-than-83 % chance that strong-to-very-strong conditions will continue through January–March 2027.
Our mountains are where winter storms can do serious damage. But there’s an important distinction between a powerful El Niño and a forecast for a powerful winter. El Niño influences the odds. What happens in Southern California depends on where individual storms travel, how much moisture they carry, and what happens when they reach California.
1982–83 and 1997–98
El Niño begins thousands of miles from California, with unusually warm ocean temperatures across the tropical Pacific. That warming changes atmospheric circulation and can shift the winter jet stream farther south, increasing the chance of Pacific storms reaching Southern California.
The winters of 1982–83 and 1997–98 are familiar examples. Both occurred during powerful El Niño events and brought widespread flooding and storm damage to California.
Still, El Niño doesn’t deliver storms on a schedule. A strong event can produce an exceptionally wet season, an ordinary one, or extended dry spells interrupted by heavy rainfall.
Our mountain ranges also respond differently. A storm that buries the San Gabriel Mountains in snow might bring heavy rain to the Santa Anas. Another could favor the mountains above Santa Barbara while leaving San Diego County relatively dry.
Elevation, temperature, wind direction, and storm track determine what happens on the ground.
The San Gabriels and San Bernardinos
The San Gabriel Mountains rise sharply above the Los Angeles Basin, putting steep canyons and mountain highways directly in the path of winter storms.
In the Angeles National Forest, heavy precipitation can swell the San Gabriel River and its tributaries, damage roads, and close popular recreation areas. Snowfall can make Mount Baldy, Wrightwood, and the higher elevations around Angeles Crest Highway difficult to reach.
The San Bernardino Mountains face similar conditions, with an added concern for communities along narrow mountain roads.
Big Bear Lake and Lake Arrowhead can receive substantial snowfall when cold Pacific storms arrive. Lower communities, including Forest Falls, Mountain Home Village, and Angelus Oaks, face a different problem when heavy rain falls on steep slopes.
Forest Falls sits along Mill Creek below the San Gorgonio Wilderness, where San Gorgonio Mountain rises to 11,503 feet. The steep drainages above the community can carry runoff, mud, and rock downhill during intense storms. The area has a long history of damaging debris flows.
Snow level will be one of the season’s most important variables. A cold storm can build the mountain snowpack, while a warmer system may deliver rain at elevations that normally receive snow. Rain falling onto existing snow can accelerate runoff and create problems downstream.
The San Jacintos, Santa Anas, and San Diego Mountains
Farther south, the San Jacinto Mountains rise above the Coachella Valley to more than 10,000 feet. Idyllwild, Mount San Jacinto State Park, and the surrounding San Bernardino National Forest can experience substantial winter snowfall.
Conditions change quickly with elevation. Rain in the valleys can accompany snow and ice on mountain trails, and access to higher elevations may become difficult during storms.
The Santa Ana Mountains, including Santiago Peak and the canyons of the Cleveland National Forest, face a different concern. Their lower elevations mean that many winter storms arrive primarily as rain.
The 2020 Bond Fire burned 6,686 acres around Silverado Canyon, and the 2024 Airport Fire spread from Trabuco Canyon toward Santiago Peak. Both left fire-damaged slopes vulnerable to erosion and debris flows. In January 2021, heavy rainfall triggered debris flows in drainages burned by the Bond Fire near Silverado Canyon.
The same concerns extend into San Diego County, where the Laguna, Cuyamaca, and Palomar mountains can receive heavy rain and snow. Sunrise Highway climbs into the Laguna Mountains, where winter storms can leave snow and ice on the road while lower elevations remain clear.
Ventura and Santa Barbara: A History of Debris Flows
The Los Padres National Forest stretches across steep terrain above Ojai and the Santa Ynez Valley. Farther west, the Santa Ynez Mountains rise abruptly above communities along the Santa Barbara coast.
In January 2018, heavy rain struck the area burned by the Thomas Fire above Montecito. The resulting debris flows killed 23 people and damaged hundreds of homes.
Wildfire removes vegetation and changes how water moves across the ground. During intense rainfall, runoff can collect loose sediment and carry mud, boulders, and trees downhill with very little warning.
That danger applies throughout Southern California’s mountains, including the San Gabriels, San Bernardinos, and Santa Anas.
When the Snow Level Rises
Atmospheric rivers are long bands of concentrated moisture that transport large quantities of water vapor across the Pacific. When they reach California, mountain terrain forces the moist air upward, often producing heavy precipitation.
An atmospheric river arriving during a cold period can deliver significant mountain snowfall. A warmer system may produce heavy rain well above the usual winter snow line.
El Niño can influence the broader storm pattern, but it doesn’t determine the strength or destination of any particular atmospheric river.
A few major storms can account for a large portion of Southern California’s annual precipitation. That makes individual storm forecasts far more useful for trip planning than the seasonal El Niño outlook.
Closed Roads and High Creeks
For hikers, campers, anglers, and off-road travelers, a wet winter can change access across Southern California’s public lands.
Forest roads may close after storms. Creek crossings that are easy in October can become dangerous in January. Trails may suffer erosion, washed-out bridges, or fallen trees. Snow and ice can remain at higher elevations long after a storm has passed.
A wet winter can replenish streams and reservoirs, improve soil moisture, and bring new growth to the mountains in spring. Cold storms can build snowpack that releases water gradually as temperatures rise.
The difference often comes down to how precipitation arrives. Moderate storms spread over several months are generally easier for the ground to absorb than intense rainfall concentrated into a few days.
Before heading into the mountains this winter, check the National Weather Service forecast for your destination, review current forest road and trail closures, and pay attention to flood or debris-flow warnings. Don’t assume a familiar route will look the same after a major storm.
NOAA’s next El Niño diagnostic discussion is scheduled for November 12. That update should give us a better picture of how the Pacific is developing as Southern California approaches its main winter storm season.
For further information, see:
NOAA’s Climate Prediction Center – El Niño/Southern Oscillation Diagnostic Discussion HERE
National Weather Service mountain forecasts — San Diego HERE
National Weather Service mountain forecasts — Los Angeles/Oxnard HERE