LOS ANGELES — Tropical Storm Rachel brings with it a slew of potential hazards, including damaging coastal flooding. The National Hurricane Center warned that Rachel could pick up some strength before arriving on the West Coast — an unusual occurrence for storms in the tropical eastern Pacific. Typically, storms weaken significantly once they enter those cooler waters. But El Niño conditions ...

Domenic Hix looks back as a large wave crashes on the shoreline in Laguna Beach, California, on Oct. 9, 2026.

Allen J. Schaben/Los Angeles Times/TNS

LOS ANGELES — Tropical Storm Rachel brings with it a slew of potential hazards, including damaging coastal flooding.

The National Hurricane Center warned that Rachel could pick up some strength before arriving on the West Coast — an unusual occurrence for storms in the tropical eastern Pacific.

Typically, storms weaken significantly once they enter those cooler waters. But El Niño conditions and an ongoing marine heat wave have pushed ocean temperatures 10 to 13 degrees higher than normal, providing a far-more-conducive environment for Rachel.

“It’s notable that this is an unusual event that’s being made possible by both coincidence of this early arriving low-pressure trough off the coast of California and the record warm — and I do mean record warm — ocean temperatures off the coast of California right now,” UC Agriculture and Natural Resources climate scientist Daniel Swain said during a briefing Friday.

Rachel is expected to make landfall either in northern Baja California or San Diego County as early as Saturday night.

In the modern record, only two storms have passed through the state at tropical-storm strength.

The first — nicknamed El Cordonazo, or the Lash of St. Francis — hit Long Beach and San Pedro in September 1939. It dumped 5.62 inches of rain on L.A. over three days, spawned wind gusts of up to 65 mph and resulted in 45 deaths from flooding, with an additional 48 deaths at sea.

There was also Nora in September 1997, which was briefly at tropical storm strength as its center passed along the California-Arizona border, but California was spared the kind of damage it delivered to Baja California. Street flooding was reported in Imperial County, the Coachella Valley and San Diego, while big waves boosted by Nora and another storm sent breakers crashing into beachfront properties in Seal Beach, seriously damaging three homes and resulting in minor damage to 45 others.

Where is flooding most likely?

The National Weather Service office in San Diego on Friday issued a rare tropical storm watch for most of San Diego County, including San Diego, Chula Vista, Carlsbad and Oceanside, meaning that tropical storm-force winds are possible over the next 48 hours. It’s only the second time a tropical storm watch has been issued in California.

Coastal flooding will remain the biggest concern for the region in the coming days, particularly for south-facing shores, given the combination of high tides, a higher-than-typical water level and the arriving tropical storm. Swells will not only bring the potential for water intrusion, but also hazardous surf — ranging from 3 to 6 feet in some areas — and rip currents, according to the weather service.

Officials had predicted that tides in Southern California would be 1 foot to 1.5 feet above normal what would ordinarily be expected without the abnormally warm ocean temperatures wrought by El Niño.

Around 9 a.m. Friday, the high tide in San Diego and La Jolla was coming in 17 inches higher than the official prediction, which doesn’t account for hotter-than-normal ocean waters or swells from tropical storms, according to NOAA’s tide forecasts. Tides were coming in 16 inches higher than the official prediction in Santa Monica and 14 inches higher in San Francisco as of Friday morning.

“We’ve got water that’s already high and then we’re going to have periods of high tides each morning and evening and then on top of that we have high surf,” said Miguel Miller, a meteorologist with the National Weather Service in San Diego. “We have all these things stacking up on each other and we’ve already seen in recent weeks how just the high tides, even without the large surf, is putting water into places where it doesn’t usually go.”

A coastal flood advisory for Ventura, Los Angeles, Orange and San Diego counties — warning of the potential for flooding in beach parking lots, boardwalks and roads, with isolated road closures expected, along with minor coastal erosion — is expected to remain in effect through Tuesday afternoon.

Coastal cities including Laguna Beach, Newport Beach and Long Beach have already seen significant flooding. Long Beach issued a mandatory evacuation order for residents of Seaside Walk between 64th and 66th Place.

How much rain is expected?

While tropical moisture from the remnants of Rachel is expected to deliver only light rain to much of Southern California between Sunday morning and Monday night, the Mojave Desert, the Inland Empire and portions of San Diego County could see more significant precipitation.

The weather service is warning that there is a moderate, or 40% chance, of excessive rainfall that could lead to flash flooding in places like San Diego, El Cajon, Chula Vista, Escondido, Palm Springs and Twentynine Palms. A moderate risk means that numerous flash floods are likely, and that many streams may flood. There is a chance that the San Diego River near Fashion Valley could reach minor flood stage.

There’s also a 15% chance of that occurring in Oceanside, San Clemente, Laguna Niguel, Riverside, San Bernardino, Las Vegas and the California-Arizona border; and a 5% chance in places like Huntington Beach, Santa Ana, Long Beach, Anaheim, Pomona, Victorville, Barstow, and most of Arizona and southern Utah.

In Los Angeles County, rain is expected to be light to moderate, ranging from about a quarter of an inch to an inch across much of the region. A bit more rain is expected in the San Gabriel Mountains, according to the weather service office in Oxnard. Rain rates are probably going to be a quarter of an inch per hour or less, making debris flow and landslides unlikely.

A bit more rain is expected in Orange County with coastal areas receiving from half an inch to an inch over the weekend and into early next week. Coastal sections of San Diego County could see between an inch and an inch and a half of precipitation with higher rain levels predicted farther inland.

El Niño impact

Nora arrived during a “very strong” El Niño season. That pattern is linked to above-average hurricane activity in the eastern Pacific, and also is usually tied to above-average rainfall for Southern California in the winter.

That climate pattern sees the heating of ocean waters in the central and eastern equatorial Pacific, which spur changes in the atmosphere that can affect weather around the world.

The National Oceanic and Atmospheric Administration’s Climate Prediction Center said Thursday that there is virtually a 100% chance that the El Niño this season will be categorized as “very strong.” There’s also an 83% chance that this El Niño will be the strongest on record, which goes back to 1950, up from a 75% probability forecast last month.

“With an event of this magnitude, the chances of experiencing impacts consistent with El Niño are larger, though not guaranteed,” the Climate Prediction Center said Thursday.

There have been only four “very strong” El Niños in the modern record — 1982-83, 1991-92, 1997-98 and 2015-16. Two of them — in 1982-83 and 1997-98 — deluged downtown Los Angeles with more than 30 inches of rain, more than double the area’s average annual rainfall.

The “very strong” El Niño of 2015-16 was a dry one for Southern California, with downtown L.A. getting only half its annual rainfall. But it did coincide with record coastal erosion along many California beaches, according to the state Coastal Commission.