A lot has been written about how this year’s Super El Niño is likely to be the strongest on record and could result in extreme weather through 2027. But we’re just learning now that it may cause serious damage to California’s coast, impacting sea levels and possibly triggering floods.

El Niño is forecast to raise sea levels along California’s coast by about a foot by the middle of next month, according to oceanographer Dillon Amaya at North Carolina State University, CNN reported. That’s because the climate pattern will push water from Mexico and Central America north up to the U.S. coastline.

That may in turn trigger “Kelvin waves”—which unlike typical waves, “slosh up and down, like water in a bathtub,” where they are, in effect, stuck, according to CNN.

“Typically, we think of El Niño and its impact on precipitation, but some of the first indications that El Niño is really occurring are the arrival of these coastally trapped waves,” Amaya told CNN.

At the same time that El Niño is expected to produce those waves and higher sea levels, California is also expecting regularly occurring King Tides, or “astronomically high tides,” climate scientist Daniel Swain at the University of California Agriculture and Natural Resources told American Community Media.

As a result, Swain said there is an elevated risk of coastal erosion and severe flooding around the San Francisico Bay Area, for low-lying towns and communities sitting six feet or less above sea level.

“El Niño doesn’t guarantee a wet winter in California,” he said. “But a very strong, potentially historically strong event, which is our expectation for this year, likely increases the amount of precipitation that California will experience this winter.”