San Mateo County sounds early alarm over winter storms as strong El Niño becomes increasingly likely
San Mateo County, California – San Mateo County is preparing for a winter that could bring more than just heavy rain. Flooded neighborhoods, damaged roads, landslides and widespread power outages are among the threats officials fear as a potentially powerful El Niño develops in the Pacific.
And with the worst weather still months away, county leaders have a message for residents: preparing after a storm warning arrives may already be too late.
The San Mateo County Board of Supervisors took an early step Tuesday, proclaiming a local emergency to strengthen preparations for the 2026-27 winter storm season. The declaration is intended to help county departments coordinate their response while encouraging households, businesses and visitors to recognize the potential dangers.
The concern is supported by recent climate projections. According to an October 8 outlook from the National Oceanic and Atmospheric Administration, El Niño is strengthening, with a greater than 83% probability of becoming a strong to very strong event during January through March 2027.
El Niño occurs when ocean waters in the tropical Pacific become unusually warm, a pattern that can contribute to wetter and stormier conditions across California.
For San Mateo County, that could mean dangerous conditions stretching from coastal communities to inland neighborhoods.
“Our county staff take preparing for severe storms seriously, and we need all county residents to know that they should, too,” said Board President Noelia Corzo.
“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.”
County officials are particularly worried about situations where multiple hazards develop simultaneously.
“The greatest danger is not any single hazard but the combination of multiple hazardous conditions,” County Executive Mike Callagy said.
“A storm arriving on a high tide, heavy rain falling on saturated hillsides, and wind damage during flooding each compound the others.”
To address those concerns, the County Department of Emergency Management will coordinate preparations alongside local agencies and county departments.
A newly established task force will monitor readiness efforts, share information and support communities ahead of severe weather. Caltrans, PG&E and other organizations may participate.
Preparations will include inspecting equipment, clearing drains and culverts, identifying sandbag locations and making sure emergency information reaches residents in multiple languages. Cities, towns and special districts will also be encouraged to strengthen their own plans.
Supervisor Ray Mueller, whose district includes much of the coastline, warned that the upcoming season could have serious consequences.
“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.
Residents are being encouraged to assemble emergency supplies, including drinking water, food, medications, batteries and flashlights. Officials also recommend checking flood and landslide risks, clearing household gutters where safe, securing outdoor belongings and discussing evacuation plans with family members.
Households should review their insurance coverage, including whether additional flood insurance is appropriate. Renters are also encouraged to consider coverage for personal belongings.
Residents can register for emergency notifications through SMC Alert, monitor weather forecasts and follow official evacuation instructions.
For county leaders, the immediate priority is simple: reduce the damage before dangerous weather has a chance to strike.
