Scientists Warn This Year's El Niño Can Trigger Unprecedented Flooding

Here are the morning’s top stories on Wednesday, September 16, 2026

• Federal scientists now say it’s very likely that a strong El Niño will continue through the end of the year. The natural phenomenon is pushing a massive stretch of warm water toward California, and climate scientists worry that this process could trigger monumental flooding later this year.
• California just became the first state in the nation to pass rules that require insurance companies to address smoke damage after major fires.
• Backers of a November ballot measure that would levy a tax on billionaires are facing an uphill battle, according to a new poll released today.

Derek Bentley is practicing karate on new blue mats in his San Rafael studio. His business is just yards from a marina connected to San Francisco Bay. The building flooded through seams in the foundation during a January storm, stacked on top of a king tide. Some of the old dirty mats are still stacked in a corner.

“We were closed for about a week after the flood and then we opened but we had like air dryers and some of the mats were still wet,” said Bentley. “Took a little bit of a credit card to it, but we got some new mats finally. We’re slowly rebuilding.”

He fears that a very strong El Niño will raise water levels and steer storms toward the Bay Area.

As for his worst fear, Bentley says, “That this place goes completely under water.”

Climate scientists warn the effects of El Niño could result in unprecedented flooding around the region. Warm water expanding could contribute several inches of temporary sea-level rise. Plus, a slow-moving pulse of water, known as Kelvin waves, could cause a rise of up to 9 inches or more over days or weeks.

Daniel Swain is a UC system climate scientist Daniel Swain says we could see potential for record-breaking water levels in some areas.

Add changes in pressure, a storm surge, and natural king tides, which will be among the highest on record in December, and Swain says some places could experience as much as 5 – 6 feet of temporary inundation above historical high tide levels at times.

“Anything that’s tidally influenced will be affected. You’re also generally going to see that all the way inland into the Delta to Stockton.”

The high water has already begun and is about 6 inches above normal at the tide gauge near the Golden Gate Bridge. Sean Vitousek is a research oceanographer at the U.S. Geological Survey.

“And that’s partially because of El Niño,” he said. “And they will probably get larger in the winter as you get more of the storm surge effects.”

To find out how cities are preparing, KQED checked in with officials across the region. Up north, San Rafael is coordinating with critical agencies to enable quick road closures. Kate Hagemann is the city’s climate adaptation resilience planner.

“That unfortunately doesn’t reduce the risk that those roads flood or those facilities are impacted.”

Travel south to the island city of Alameda, and officials are beginning to service pumps, clear out storm drains and prepare barricades. Erin Smith is the city’s public works director.

“We have a vacuum truck that’s able to quickly dislodge material that may be preventing the storm water from flowing.”

Head west to San Francisco and officials are planning similar steps along a stretch of seven and half miles of shoreline. Crews will prepare sandbags, stage pumps and plan traffic detours. Brad Benson is with the Port of San Francisco.

“The king tides and these El Niño events are a glimpse into the future. Some of these areas, we have very important assets,” said Benson, referring to Muni and public spaces like the Ferry Building.

If you drive west until you reach the Golden Gate Bridge, you’ll find the Pacific Ocean forcing waves into San Francisco Bay. Kristina Hill and I chatted near Fort Point, with a view of San Francisco’s seawall, beaches and skyscrapers. Hill studies sea-level rise at UC Berkeley and thinks the temporary high-water line could expose weaknesses in the Bay Area’s human-made barriers meant to keep water out.

“We’ve been trying to fill the cracks in the bathtub by putting out little informal levees, and then occasionally a very big project like the San Francisco seawall,” said Hill.

She says flooding this winter could show decisionmakers that it’s time to think about long-range solutions differently.

“And the things we’ve done in the past to prevent coastal flooding won’t work when that water doesn’t go back down again.”

Hill added that higher water levels are predicted to become an everyday reality in just a couple of decades.

Governor Gavin Newsom signed Assembly Bills 1642 and 1795, which will require insurers to test for smoke damage, cover the cost of cleaning contaminants like lead and asbestos, and keep paying for a homeowner’s alternative living expenses until the home is found safe to reoccupy.

The California Department of Toxic Substances Control will have until the end of 2028 to develop testing and cleaning standards for lead and asbestos, and until the end of 2029 to set rules for heavy metals and other pollutants.

The change comes after the L.A. County fires last year, which left thousands of homes standing, but covered in toxic fire residue. Homeowners have been fighting their insurers to cover the cost of dealing with smoke damage.

According to the state Department of Insurance, property owners filed 13,000 smoke damage claims for standing homes after the January 2025 fires. While insurers have covered testing and cleaning in many cases, other homeowners are still unable to return home as they battle with insurance companies over addressing smoke damage.

Insurance industry groups fought the new rules, saying they opposed shifting regulation away from the state Department of Insurance and to the Department of Toxic Substances Control.

But proponents say they’ll help families displaced by future fires get home faster.

Voters will weigh in Nov. 3 on Proposition 40, which would impose a one-time, 5% wealth tax on billionaires who lived in California as of Jan. 1, 2026. The tax is estimated to raise up to $100 billion and would be used to offset deep federal healthcare cuts imposed last year by Congress.

The poll by the Public Policy Institute of California found 52% of likely voters saying they will vote yes on the billionaire tax, known as Proposition 40, with 46% opposed.

That’s a slim margin to begin with — but the survey also found voters narrowly lining up behind two ballot measures that could nullify the billionaire tax.

Proposition 41, which would make any new taxes subject to the state’s existing spending limit, is leading in the Public Policy Institute of California poll 51% to 44%. Proposition 42 would prohibit taxes on financial assets such as stocks and other personal property other than real estate. It’s leading in the poll 54% to 43%.

If all three pass, but Proposition 41 or 42 gets more votes than Proposition 40 gets, the state will be prohibited from enforcing the billionaire tax.

Mark Baldassare is the Public Policy Institute’s statewide survey director.

“So the supporters [of Proposition 40] have the work to do of both keeping their support, which is now just above 50%, in the majority range, and also raising questions about Propositions 41 and 42 that may reduce support below what Proposition 40 is getting,” Baldassare said.

That task will likely be made even harder by the large amount of money being spent by billionaires against the proposed wealth tax: Opponents of the billionaire tax have already raised nearly $120 million to fight Proposition 40 and support Propositions 41 and 42.

In all, California voters will weigh in on 14 ballot measures this fall, and PPIC found voters “exhausted” by the responsibility: Nearly 80% of respondents said they’re frustrated with the size of the ballot.