Such high-tide flooding that inundates roads and buildings along the west coast of the Americas tends to be uncommon outside of El Niño years, but that could change by the 2030s.

An analysis by NASA’s sea level change science team finds that if a strong El Niño develops this winter, cities along the western coasts of the Americas could see an increase in the frequency of high-tide flooding that can swamp roads and spill into low-lying buildings.

El Niño is a periodic climate phenomenon characterized by higher-than-normal sea levels and warmer-than-average ocean temperatures along the equatorial Pacific. These conditions can spread poleward along the western coasts of the Americas. El Niño, which is still developing this year, can bring more rain than usual to the U.S. Southwest and drought to countries in the western Pacific like Indonesia. These impacts typically occur in January through March.