Mark Merrifield, director of the Center for Climate Change Impacts and Adaptation at the UC San Diego Scripps Institution of Oceanography, made the assessment during a recent online town hall. “We’re expecting likely the highest sea levels ever recorded on the California coast associated with this event,” he said.

California Coast Faces Highest Sea Levels on Record This Year

NASA satellite data presented by Merrifield showed sea levels in the eastern Pacific already more than half a foot above the reference state. He said that by fall and winter of 2026, levels along the California coast should climb “far above the average seasonal cycle.”

How El Niño Raises Sea Levels

El Niño develops when sea surface temperatures in the central and eastern tropical Pacific rise significantly above average. The warmer water expands, and shifts in atmospheric circulation help push higher water toward the Americas. In California, past strong El Niño events have produced temporary sea level increases of roughly half a foot to a foot above normal seasonal levels, particularly around San Francisco.

This year’s event is projected to be among the strongest in decades. Forecasters have described it as potentially historic in intensity. The elevated water levels will sit on top of the steady rise driven by climate change over the past century. In addition, the natural tidal cycle is expected to reach peak “king tides” near the end of the year, creating what Merrifield called an “unlucky coincidence.”

Areas at Risk: El Niño Could Push California Sea Levels to Record Highs

Higher sea levels are expected to affect the entire California coast, from the San Francisco Bay Area south to San Diego, and could influence the Sacramento-San Joaquin Delta. When combined with winter storms or large waves, the elevated baseline increases the chance of flooding in low-lying neighborhoods, erosion of beaches and bluffs, and saltwater intrusion into groundwater and wetlands.

Scientists note that even without major storms, higher king tides alone may cause more frequent nuisance flooding in places already vulnerable. Historical El Niño winters have demonstrated these effects; the current combination of factors raises the possibility of setting new local water-level records.

Broader Context El Niño Could Bring California Its Highest Sea Levels Ever Recorded

El Niño is a natural climate pattern, but its impacts occur against a backdrop of ongoing global sea level rise. Warming oceans expand and melting ice sheets and glaciers add volume. California has already experienced measurable increases over recent decades, making temporary spikes more consequential than in the past.

Researchers emphasize that the exact height of peak water levels will depend on the final strength of the El Niño, the timing of storms, and local factors such as land subsidence. Preparation efforts, including early warning systems and coastal management planning, are being discussed as the event continues to develop through the remainder of 2026 and into early 2027.

Key Takeaways

• Scientists expect the current El Niño to produce the highest sea levels yet recorded on the California coast this fall and winter.
• Temporary rises of roughly 6–12 inches above seasonal averages are typical for strong events and will add to long-term climate-driven rise.
• King tides peaking late in the year and possible storms increase the likelihood of coastal flooding and erosion.
• Effects could stretch from the San Francisco Bay Area to San Diego and the Sacramento-San Joaquin Delta.
• Monitoring and preparation are underway as the event strengthens.

Fact Check Notes

Confirmed facts

• Mark Merrifield of Scripps Institution of Oceanography stated that the highest sea levels ever recorded on the California coast are likely with this El Niño (reported August 2026).
• Sea levels in the eastern Pacific were already more than half a foot higher than the reference state according to NASA satellite data cited by Merrifield.
• Historical strong El Niño events have raised San Francisco sea levels by about 0.5 to 1 foot above seasonal norms.
• The rise is temporary and related to thermal expansion and ocean dynamics associated with El Niño.
• King tides are expected to peak near the end of 2026.

Claims that should be attributed

• Statements about “highest sea levels ever recorded” and the expected timing come directly from Mark Merrifield and related scientific presentations.
• Broader forecasts of El Niño strength come from NOAA and other climate model consensus reports.