Much of Marin's shoreline was once tidal marsh. Today, neighborhoods built on that low ground, from the Canal in San Rafael to the bay flats of Corte Madera, the Greenbrae Boardwalk, Belvedere Lagoon, Sausalito's waterfront and Stinson Beach, can see water from two directions at once: rain falling on the land and high tides pushing in from the bay or ocean. When a big storm arrives during the highest tides of the year, the combination can overwhelm drainage.
Water has nowhere to go. Storm drains in bay-edge neighborhoods discharge to the bay. When the tide is very high, outflow slows, and some areas rely on pump stations and levees to stay dry.
Groundwater sits high. In former marshland, the water table can be close to the surface, so crawlspaces and slab edges stay damp in wet months.
Salt matters. Saltwater intrusion and salty air corrode metal, including fasteners, electrical connections and HVAC components, faster than inland.
Timing matters. The highest winter tides in the Bay Area typically occur around new and full moons in winter months. A storm that coincides with a high tide is the scenario to plan for. Check tide tables alongside the National Weather Service Bay Area forecasts when big storms are coming.
As of the Climate Prediction Center's October 8, 2026 ENSO discussion, an El Niño Advisory is in effect, and NOAA says a strong-to-very strong El Niño is likely through January–March 2027. NOAA is also careful to say that a stronger event makes El Niño-like impacts more likely, not guaranteed. El Niño winters have historically tilted Northern California toward wetter conditions, but individual seasons vary, and no outlook can tell you when or where a specific storm will hit. Watch the CPC seasonal outlooks and the National Weather Service Bay Area office for forecasts as the season unfolds.
Saltwater adds steps to cleanup:
Our flood cleanup and storm damage pages describe what professional help typically involves.
Shoreline communities across Marin are planning for sea level rise, and the risks for low-lying homes are likely to grow over time. Longer-term options for homeowners can include elevating utilities, flood-resistant materials on lower floors, flood vents and better drainage. Talk to licensed professionals, and check with your city about local projects and requirements.
Low-lying neighborhoods often depend on shared infrastructure like levees, pump stations, tide gates and storm drains maintained by a city, county district or homeowners association. It's reasonable to ask: Who maintains the levee or pump station near me? Is there backup power for the pumps? Where are sandbags distributed? How will residents be notified if pumps fail or a levee is overtopped? HOAs in lagoon communities may have their own storm procedures. Knowing these answers before a storm helps you decide when to move cars and belongings and when to leave.
If your home has water damage after a high-tide storm, submit a request to connect with an independent local restoration provider. Also see our guide to mold after storms, since damp, salty crawlspaces are prime territory for mold.
The highest winter tides typically occur around new and full moons in winter; check local tide tables.
Often yes; salt residue attracts moisture and corrodes metal, so surfaces may need cleaning before drying and electrical items need inspection.
Yes; check bilge pumps and through-hull fittings and follow your marina's storm procedures.
It varies: cities, county districts or HOAs. Ask your local government or HOA.
If your street floods, moving cars to higher ground ahead of time is prudent.
This article is general information, not legal, insurance or medical advice. Sources are linked in the text.