Historic high tides flood California communities and disrupt transportation

NOAA puts December high-tide flooding risk above 80% in four areas

Historic high tides inundated streets, flooded homes and businesses, and disrupted transportation corridors and train routes across low-lying California communities from San Diego to the San Francisco Bay Area this week. The National Weather Service issued flood advisories and warnings that it said would last for days, with significant coastal flooding expected in San Diego and Orange counties through Thursday.

In Marin County, north of San Francisco, kayakers and paddleboarders crossed typically busy thoroughfares on Monday and Tuesday after a temporary lagoon formed. Several drivers had to be rescued from floating cars, while cyclists who attempted to cross the lagoon found themselves waist-deep.

In Newport Beach, seawater seeped through berms, seawalls and sandbag blockades along the shoreline, pounding emergency infrastructure set up to keep out the swelling sea.

All-time records were broken in parts of California. Near Los Angeles and San Diego, tides rose above 8 feet. San Francisco registered its highest reading for the month of October on Wednesday, breaking a record set the day before.

In its Wednesday outlook, the National Weather Service said, “Numerous roads may be closed. Low lying property including homes, businesses, and some critical infrastructure will be inundated.” Moderate flood risks extended into the weekend in Los Angeles, though tides were expected to begin dropping after Thursday. Shoreline erosion was expected along the California coast.

Records from the National Oceanic and Atmospheric Administration show Los Angeles has already logged 12 coastal flood days in 2026, outpacing any year in the last 50 with months still to go.

Experts warned that the dangers will not recede when the tides do, and that the newly set records will not be held for long. The worst flooding may be to come as severe impacts from an exceptionally strong and still-strengthening El Niño unfold in the months ahead, with the potential to raise tides several feet above the levels recorded this week.

Daniel Swain, a climate scientist, warned during an online briefing Tuesday that the current flooding could precede more disruptive conditions. “What we are seeing now could be the beginning of what could be significantly more disruptive conditions later this year,” he said.

Swain said thermal expansion from a record-breaking oceanic heatwave was layered over higher sea levels fueled by the human-caused climate crisis. A coastally trapped Kelvin wave—a massive underwater band of warm water that crossed the Pacific and moved up the North American shoreline—also contributed. He said the California coast could see more Kelvin waves through winter and into early next year. “I would expect these water levels to be exceeded multiple times this winter,” Swain said.

NOAA’s December outlook gives San Diego, La Jolla, Los Angeles and Santa Monica an above-80% chance of high-tide flooding. Most stations near coastal communities to the north, through the Canadian border, were in the 60% to 80% category.

The floods seen this week were not the so-called king tides, the highest predicted tides of the year. Those tides are expected around busy holiday weekends near Thanksgiving and Christmas, and again from January 20-23 next year.

King tides can add an additional foot or two to water levels already elevated by roughly a foot through human-caused warming and the effects of El Niño and Kelvin waves. If each of those layers aligns as expected, they could create up to 5 feet of sea-level rise above average in many places at once.

“We are well into extreme territory – and really in record-breaking territory,” Swain said. He said those conditions could set the stage for “disastrous flooding” if a storm arrived while waters were high, adding that this is when things “get really hairy.”

The historic El Niño brewing in the Pacific has the power to unleash extreme weather around the world, and in California that could mean supercharged storms. Southern California especially tends to get doused during El Niños, and this year the climate phenomenon, characterized by warmer-than-average equatorial sea surface temperatures, could pack an extraordinary punch. “There’s at least a 30-40% chance we stack all of these this winter, and potentially more than once,” Swain said.

Current advisories cover high-tide flooding through Thursday in San Diego and Orange counties and moderate risk through the weekend in Los Angeles. Swain warned more broadly that elevated water could recur throughout winter and become disastrous if a storm coincides with the highest tides.