NOAA warns that a forecast El Niño this summer could lead to frequent, widespread high-tide flooding across U.S. coasts—even without storms—because sea levels have already risen and El Niño can deepen and intensify flooding conditions.
When the next weather pattern arrives, coastal residents may not need a dramatic storm to feel the impact. Scientists at NOAA are warning that El Niño, forecast to emerge this summer, could bring frequent and widespread flooding even without the presence of storms.
For William Sweet, an oceanographer at NOAA who tracks “high tide flooding,” the danger is two layers working at once.. “It usually ends up being a double whammy,” Sweet said.. “The first punch is decades of sea level rise, which has waters close to the brim in many coastal communities.. And now with this second punch — a strong El Niño — coastal communities face more frequent. deeper and widespread high tide flooding along both the West and East Coasts.”
High tide flooding is an increasingly common problem as sea levels rise. leaving coastal regions more vulnerable to inundation simply when tides run high.. Sweet’s focus on this mechanism is part of a broader NOAA warning that ties flooding risk to the timing and intensity of the developing ENSO cycle.
El Niño is one component of the El Niño-Southern Oscillation. or ENSO. cycle. which alternates weather patterns every two to seven years. according to NOAA.. The cycle is currently in its neutral phase after transitioning out of La Niña earlier this year.. Forecasters have predicted El Niño. the warmer phase of ENSO. will emerge soon. and NOAA’s Climate Prediction Center said last week there is at least an 82% chance it will arrive by July and continue through February in the Northern Hemisphere.
NOAA also describes the chain of effects El Niño can set in motion.. As the El Niño phase takes hold. trade winds across the tropical Pacific Ocean weaken. helping warm the ocean and raise sea levels around the Americas—typically for at least several months.. During this phase, NOAA says the west coast of the U.S.. may see high tides and strong surf, while the Atlantic coast may experience more storm surge.. The agency also flags potential heavy rainfall for the southeastern and Gulf coasts. where excessive rain could add to flooding pressures.
Scientists are still determining how intense the upcoming El Niño will be.. Sweet said the El Niños that prevailed from 2015 to 2016 and 2023 to 2024 were particularly strong and resulted in upticks in high tide flooding compared with previous years—something NOAA has been tracking and trying to better understand.
NOAA has encouraged communities along any U.S. coast to stay informed using its coastal inundation dashboard, which is updated with current water levels and forecasts, along with its monthly flooding outlooks.
The pattern NOAA is pointing to is consistent: decades of sea level rise leave coastal waters close to the brim, and when a strong El Niño arrives as the second “punch,” communities face more frequent, deeper and widespread high tide flooding along both the West and East Coasts.
For now, the key uncertainty is the strength of the El Niño itself, while NOAA’s published probabilities and tools are meant to help coasts prepare for flooding risk that can be driven by tides, not just storms.
El Niño NOAA ENSO high tide flooding sea level rise Climate Prediction Center coastal inundation dashboard