You’ve probably heard by now: A strong El Niño is developing in the tropical Pacific Ocean.
So what can San Diegans expect?
El Niño can influence weather patterns around the world, but its effects on Southern California — including warmer ocean temperatures, higher sea levels and an increased likelihood of strong storms — could all affect San Diego’s coastline.
Here’s what to know.
What is El Niño?
El Niño is a large-scale change in ocean temperatures, winds and atmospheric pressure in the tropical Pacific Ocean. It can bring heavy rain and floods.
Under normal conditions, trade winds blow from east to west across the Pacific. Those winds push warm surface water toward the western Pacific, while cooler water rises near the coasts of Ecuador and Peru in a process known as upwelling.
During El Niño, those trade winds weaken or can even reverse. That disrupts the normal upwelling of cold water and allows warmer water to move eastward across the Pacific, according to UC San Diego Scripps Institution of Oceanography researcher Reinhard Flick.
For Southern California, some of the most significant effects tend to become most noticeable along the coast during the winter.
Gov. Gavin Newsom proclaimed a state of emergency in California on Tuesday amid developing El Niño conditions to help with preparedness and the protection of vulnerable communities.
Why is this one ‘very strong’?
The National Oceanic and Atmospheric Administration declares an El Niño when temperatures in the equatorial Pacific are 0.5 degrees Celsius above average for several consecutive months. A “very strong” El Niño is declared at temperatures above 2 degrees Celsius above average.
The most recent forecasts predict those temperatures will reach 4 degrees Celsius above average in November and December, as reported in The Guardian and elsewhere.
Saturday, the temperatures reached 3.05 degrees Celsius above average, eclipsing a daily record set in 2015.
A “super El Niño” refers primarily to the strength of the El Niño conditions in the tropical Pacific. The stronger the underlying conditions, the greater the potential for some of the effects associated with El Niño.
A stronger El Niño can include a greater frequency or strength of storms, Flick said.
But a very strong El Niño does not automatically mean San Diego will experience record-breaking storms or flooding.
The strength of the tropical El Niño and the conditions that ultimately develop along the Southern California coast are related, but they are not the same thing.
Experts use the 1982-83 El Niño as a benchmark for the strength of an El Niño event. The current 2026-27 event is expected to be stronger in terms of its tropical conditions. But Flick said that does not necessarily mean its impacts on the California coast will surpass those of 1982-83
That activity caused widespread flooding, beach erosion and property damage across the state, with California reporting more than $100 million in storm-related damage.
What could it mean for San Diego?
Water temperatures by the Ellen Browning Scripps Memorial Pier have been unusually warm this year, breaking numerous daily records between late winter and spring.
As El Niño develops through the fall and winter, warmer ocean temperatures can potentially affect marine ecosystems and fisheries.
But the bigger concern for San Diego’s coastline is what happens when higher sea levels meet strong storms and large waves.
El Niño can raise sea levels along the Southern California coast by several inches, according to Flick. That temporary increase comes on top of a much longer-term rise in sea level.
At the same time, El Niño also increases the probability of strong storms in the North Pacific. Those storms can bring heavy rainfall, atmospheric rivers and large waves.
Southern California is normally somewhat sheltered from North Pacific storms by Point Conception State Marine Reserve. But during El Niño events, stronger storms can track farther south and send waves toward the coast from a more westerly direction.
That can increase the potential for coastal erosion and flooding.
But the risk can increase substantially when a strong storm, large waves, high tides and climate change-related elevated sea levels coincide, according to UC San Diego Scripps Institution of Oceanography research meteorologist Alexander Gershunov.
Heads up for these local communities
Flick identified low-lying coastal areas as particularly vulnerable. These include parts of Imperial Beach, Coronado, Ocean Beach, La Jolla Shores and Del Mar, as well as vulnerable areas farther north.
The exact level of risk varies by location, with beach orientation, offshore reefs, the direction of approaching waves and the elevation of nearby development contributing to it.
Low-lying developed areas are especially vulnerable because flooding and erosion can damage buildings, roads and other infrastructure.
Some of the highest tides are expected around Thanksgiving and Christmas Eve and in late January. The projected peak high tide around Christmas Eve will eclipse 7 feet, while other winter peaks will approach about 7 feet, according to NOAA.
A major storm that occurs at roughly the same time could have a greater coastal impact.
How San Diego is preparing
San Diego County officials say preparation for severe weather happens year-round.
The county’s Public Works Department maintains nearly 2,000 miles of roads and 19,000 culverts in unincorporated areas, and crews inspect and clean storm drains and culverts, sweep streets, trim trees and repair roads ahead of storm season.
The county also has 13 road maintenance stations throughout the unincorporated area and stages materials in them to help respond to weather-related emergencies.
During an emergency, the county’s Office of Emergency Services will issue alerts and warnings through tools including the Alert San Diego and the Genasys Protect apps.
County officials recommend that residents prepare before a storm rather than wait for severe weather to arrive. That means checking private drains, gutters and drainage areas for debris; identifying areas around your property where water could collect or soil could erode, and knowing where to get sandbags.
You don’t have to wait for a storm to figure out what to do. The county recommends several resources that can help San Diegans understand their risks and receive updates during severe weather.
San Diego County’s El Niño preparedness guide has information on flood risks, emergency alerts, sandbags and home preparations. The city of San Diego’s own El Niño guide also breaks down potential impacts, including flooding, coastal erosion and heavier rain, along with steps residents can take before a storm.
