August 11, 2026 — A strengthening El Niño could bring the highest sea levels ever recorded to the California coast this year, raising the risk of widespread and damaging flooding.
It’s the latest effect forecast for what’s expected to be an historically strong event, one forecasters warn could also lash Southern California with powerful rain and broil both land and sea with punishing heat waves.
“We’re expecting likely the highest sea levels ever recorded on the California coast associated with this event,” said Mark Merrifield, director of the UC San Diego Scripps Institution of Oceanography’s Center for Climate Change Impacts and Adaptation.
During a recent online town hall, Merrifield presented a NASA satellite image showing sea levels already more than half a foot higher in the eastern Pacific Ocean compared to the reference state, and said by this fall and winter, “we should be seeing sea levels far above the average seasonal cycle.”
According to NASA, El Niño’s warmer ocean water displaces colder water close to the sea surface. Warmer water causes a rise in the sea surface height because water expands as temperature rises.
Data collected by scientists over the years also have shown how El Niños contribute to “enormously strong” waves, which can cause beaches to “erode and to narrow,” Merrifield said. “It’s well documented that during El Niño events, beaches across the entire state tend to move landward by about 30 meters [98 feet] or so.”