El Niño and King Tides: What to Know This Winter

What We Know Now

El Niño is here and getting stronger. NOAA’s Climate Prediction Center has an El Niño Advisory in effect.
King Tide dates are already set. They’re based on the sun and moon, not the weather.
The state declared an emergency. On September 21, 2026, Governor Newsom proclaimed a statewide State of Emergency for El Niño preparedness. This helps local agencies like the City move faster to strengthen readiness before severe weather this year.

King Tide Windows

San Mateo County is planning around these dates:

November 2026: Nov. 24 to 26
December 2026: Dec 22 to 25
January 2027: Jan 20 to 23

A storm arriving during one of these windows is the main scenario the county is preparing for.

What’s Forecast (Could Change)

NOAA says a strong to very strong El Niño is likely through this winter and gives an 83% chance this fall's event will be the strongest since 1950.
Above normal rain is favored for much of coastal California from December through April, with the greatest odds in January through March.
Effects should build slowly in late fall and pick up in mid to late winter.
NOAA says El Niño “raises the odds” of these impacts, but doesn’t guarantee them.

What It Means for San Mateo County

Rain flooding is harder to predict. It depends on individual storms, which can’t be forecast weeks out. San Mateo County Emergency Management will share storm updates as forecasts firm up.
Stay alert through March. A quiet December doesn’t mean El Niño fizzled.
Coastal flooding is a big risk, but flooding can happen anywhere, including San Mateo. We know the King Tide dates ahead of time, and El Niño tends to raise water levels along the coast. We recommend preparing now in case we see flooding.

Get Ready Now

Make a plan. Know how your household will stay in touch and where you’ll go if you need to leave.
Build a kit. Pack water, food, medications, flashlights and chargers.
Get sandbags. Pick them up before the first big storm, not during it. Our self-serve sandbag stations are open to City of San Mateo residents during the wet weather season. For more info on free sandbags, visit www.cityofsanmateo.org/stormprep.
Sign up for SMC Alert. Get emergency alerts by text, email or phone at https://www.smcalert.info/.

Stay Safe in a Storm

Don’t drive or walk into flood water.
Just 6 inches of moving water can knock you off your feet.
12 inches of water can carry away most cars.
Keep generators at least 20 feet from your home, and away from doors and windows.

Learn More

For forecasts, preparedness tips and storm updates, visit the San Mateo County Winter Weather Preparedness page.

Frequently Asked Questions
Important Resources

Does the Governor's emergency mean the county is getting money?

The Governor's September 21, 2026, proclamation directs state agencies to prepare, stage resources, and speed up permitting. It doesn't bring local funding or make any finding about San Mateo County. It matches the readiness work already underway here.

Is this a super El Niño?

NOAA says a strong to very strong El Niño is likely through this winter and gives an 83% chance this fall's event will be the strongest since 1950. That raises the odds of a wetter, harder winter. It doesn't tell us which storms, when, or where. Getting ready now pays off either way.

Will it be like 1998 or January 2023?

No one can say that yet, and past winters aren't a forecast. What we do know is when the King Tides arrive and what each household can do today.

Where do I get sandbags?

The City has three self-serve sandbag stations:

Corp Yard - 1949 Pacific Blvd
Beresford Park Parking Lot - 2720 Alameda de las Pulgas
Anchor Road/Bay Trail Parking Lot - Anchor Rd at 3rd Ave./J. Hart Clinton Drive

Learn more about where and when sandbags are available.

How will I know if I need to leave?

Sign up for Nixle, SMC Alert at smcalert.info, look up your zone at protect.genasys.com, and follow the City of San Mateo on our social media channels.

What's the county doing?

San Mateo County Emergency Management is tracking storms with UC San Diego's Scripps CW3E and the National Weather Service, coordinating with every city and response partner in the county, and aligning alerts and warnings across agencies.

What’s the city doing?

To learn more about how the City is preparing for the wet weather, we encourage residents to listen to the Public Works’ department “Wet Weather Preparations – Update” informational presentation to City Council on November 2, 2026. Following the meeting, a recording will be available on the City’s YouTube page.

Should I buy flood insurance?

We can't advise on individual policies. Most home and renters policies don't cover flooding, and new flood policies usually take 30 days to start. Talk to your agent or visit floodsmart.gov.

Learn more about what the City of San Mateo has done to reduce flood risk.