Updated Thursday, October 15, 2026.
You cannot see it from the shore, and you could not feel it on a boat. But a slow pulse of warm water born thousands of miles away near Indonesia has been creeping up the West Coast this month, lifting the sea by an estimated 6 to 12 inches as it goes.
It has already passed California, where around 20 homes were evacuated in Long Beach in September after heavy surf flooded a seaside neighborhood, and it is now moving through Oregon on its way north.
On Monday, the National Weather Service warned of a moderate risk of sneaker waves along the southern Oregon coast, covering Douglas, Coos and Curry counties and reaching into Northern California. Forecasters say the pulse does not create those waves. What it does is change how far they can reach.
What a Kelvin Wave Actually Is
A Kelvin wave is less a wave than a slow sloshing of the ocean. According to NOAA oceanographer William Sweet, it forms along the equator in the western Pacific when trade winds slacken, a pattern tied to El Niño.
Warm water that has piled up in the western Pacific then drifts east, and when it reaches the Americas, part of its energy turns and travels north along the coast as what scientists call a coastally trapped Kelvin wave.
The Associated Press reports that this pulse is moving up the coast at about 6 miles per hour, or roughly 150 miles a day, and that more are coming.
NOAA Fisheries confirmed on October 6 that one wave was already making its way up the North American coast, with one or two more still in the tropics, and experts expect the passes to continue between October and February.
Models shared by the National Weather Service office in Medford showed the first arriving on the southern Oregon coast during the first to second week of October, and elevated water levels are expected to persist until El Niño weakens in the spring.
NOAA research oceanographer Michael Jacox has stressed that the pulse alone will not flood anything. Its significance is that it lifts the baseline. The water that tides, storm surge and big swells have to build on is suddenly 6 to 12 inches higher.
It Does Not Make Sneaker Waves. It Makes Them Reach Farther.
That distinction matters, because sneaker waves have their own cause. The National Weather Service says they tend to develop when a distant offshore storm generates swell with a very long period, often more than 15 seconds between crests, which lets waves carry enormous energy before they reach shore. The waves can arrive as ordinary large breakers or as a sudden surge that runs far beyond the previous ones.
A higher sea does not change that physics, but it changes the geometry. With the water table of the ocean raised by up to a foot, the wash from every wave starts higher on the beach.
Meteorologists in Medford warned that when the Kelvin wave pairs with a storm or king tides, the result can be very high water, with waves reaching farther than they used to and eating away at dunes.
El Niño winters also tend to bring larger-than-average swells from the North Pacific, and the largest tides of the year, the spring and king tides, run from October through February.
Coastal scientists quoted by the AP say that combination can cause exceptional erosion along the West Coast.
For the person standing on a beach, that translates into a simple rule: the usual sense of where the safe line is no longer holds.
Why Oregon’s Beaches Are Especially Unforgiving
Oregon’s coast is public and spectacular, which is exactly why it draws crowds, and its geography stacks the odds against anyone caught out by a surge.
- A long run-up. The National Weather Service says sneaker waves can wash more than 150 feet up a beach. Its beach hazard statements carry a blunt reminder: no place on the beach is too high for a wave to reach.
- Little warning. There can be 10 to 20 minutes of small, harmless-looking waves before a sneaker wave strikes, the agency says. They are named for that habit of appearing without warning after a long stretch of quiet surf.
- Driftwood. Oregon’s beaches are scattered with heavy logs that weigh hundreds of pounds when soaked, and a surge can lift them, roll them up the beach and roll them back down. In 2019, a woman was seriously injured at Nehalem when a wave flipped the log she was sitting on and pinned her beneath it.
- Debris and cold. Sneaker waves carry sand and gravel that can fill a person’s clothing and drag them down, and the Pacific is cold enough to cause cold-water shock and exhaust even strong swimmers within minutes.
- Rocks, jetties and headlands. Waves can sweep over them in seconds, and these are the places the weather service repeatedly tells visitors to avoid.
The toll is real. Oregon recorded 21 deaths attributed to sneaker waves between 1990 and March 2021, most of them between October and April, according to reporting compiled from The Oregonian.
In 2020, two children died after a sneaker wave swept them off a beach trail. The National Weather Service has said that sneaker waves have killed more people on the West Coast than all other weather hazards combined.
What to Do
The guidance from the weather service is consistent, and it applies whether or not a Kelvin wave is passing:
- Never turn your back on the ocean.
- Stay off logs, rocks, jetties and headlands near the water, and keep children and pets well away from the surf zone.
- Check National Weather Service alerts and tide forecasts before heading out, and take a Beach Hazards Statement seriously. The weather service says sneaker waves are most likely to run far up the beach around high tide.
- Do not treat a few quiet minutes as proof the water is calm, since the lull is part of the pattern.
A Winter-Long Window
The pulse itself will move on, and the next one is already on its way. NOAA Fisheries notes it also matters beyond the beach: warm El Niño water can bring plankton with less fat to the Oregon coast, which is a poor food supply for young salmon heading out to sea.
For visitors, the message is simpler. This is the season when sneaker waves are most likely to turn deadly in Oregon, and for the next few months the ocean is starting each day a little higher than usual.
Sources: National Weather Service (Portland and Medford offices) beach hazard statements and sneaker-wave guidance, as reported by KOIN, KGW, KING 5 and Hoodline; Associated Press (Martha Bellisle), “What to know about the Kelvin wave raising the sea level along the West Coast,” October 3, 2026; KOBI-TV NBC5, “Kelvin wave to raise sea level on the coast,” September 30, 2026; National Geographic, October 6, 2026; U.S. News & World Report, October 1, 2026 (NOAA’s William Sweet); NOAA Fisheries explanation of October 6, 2026, as summarized by Surfside WA News, October 9, 2026; Yahoo News/Oregon coast sneaker-wave alert, October 12, 2026; Wikipedia’s compiled entry on sneaker waves, citing National Weather Service materials and The Oregonian (April 2021).
