REDWOOD CITY, CA — San Mateo County officials are preparing for a potentially powerful El Niño season that could bring heavy rain, flooding, landslides, coastal erosion, high winds and power outages this winter, urging residents to prepare before severe weather arrives.
The Board of Supervisors on Tuesday proclaimed a local emergency to coordinate preparations for the 2026-27 storm season. The action comes as federal forecasters report a strengthening El Niño, which can influence winter weather patterns across California.
According to the National Oceanic and Atmospheric Administration's Oct. 8 outlook, there was a greater than 83 percent chance of a strong to very strong El Niño through January-March 2027. El Niño is a climate pattern involving unusually warm ocean waters in the tropical Pacific that can affect weather around the world.
California's outlook remains uncertain, however, and a strong El Niño does not guarantee that every part of the state will experience a wetter-than-normal winter. Recent Patch coverage has explored what previous strong El Niño years could mean for California's 2026 winter and the questions forecasters are weighing about how the developing pattern could affect Northern and Southern California.
"We can all take actions, now, to prepare our families and our homes; none of us should wait until there is a major storm in the forecast," said Board President Noelia Corzo.
The county's Department of Emergency Management will lead storm preparations alongside county departments and local agencies. A new task force will coordinate readiness efforts, track progress and share information with communities. Caltrans, PG&E and other agencies may also participate.
Preparations include clearing drains and culverts, checking equipment and preparing sandbag locations. The task force will also work to make emergency alerts and safety information available in multiple languages and keep county leaders updated as conditions change.
Supervisor Ray Mueller, whose district includes much of the county's coastline, said the season could pose significant risks if major storms hit the region.
"This year's El Niño has the potential to be historic in its severity and impact, should storms hit our County and our Coastline," Mueller said. "We have the invaluable opportunity right now to lessen the damage it will cause to our health and community. Everyday counts."
Mueller warned that residents could face road closures, power outages and periods of isolation if storms disrupt transportation and utilities.
County Executive Mike Callagy said officials are concerned about the combined effects of multiple hazards, particularly when storms coincide with high tides or heavy rain falls on already saturated hillsides.
"The greatest danger is not any single hazard but the combination of multiple hazardous conditions," Callagy said. "A storm arriving on a high tide, heavy rain falling on saturated hillsides, and wind damage during flooding each compound the others."
The county is also encouraging cities, towns and special districts to complete their own storm preparations and share readiness information with residents.
Officials recommend that residents take the following steps before winter storms arrive:
The Board of Supervisors' local emergency proclamation is intended to help coordinate countywide preparations for the 2026-27 storm season.
Sign up for free local newsletters and alerts for the
Redwood City Patch
Patch.com is the nationwide leader in hyperlocal news.
Visit Patch.com to find your town today.