Are King Tides Dangerous? Flooded Roads, Waves and What to Avoid

Are king tides dangerous? For most people a king tide is a spectacle rather than a threat, but it brings three real hazards: salt water standing on low roads, flooded parking lots and paths, and winter surf breaking on top of an already high tide. The water will not rise fast enough to catch you on a sidewalk. People get hurt driving into water they cannot read, standing on rocks when a wave arrives, or walking back to find the tide has covered the way out.

The tide is the easy part to plan for. King tides in Marin show up on NOAA charts months ahead, so you can know the hour of the peak before you leave the house. The weather riding on top of it is the part nobody can predict that far out, and weather is what turns a high tide into a flood.

Are King Tides Dangerous to Drive Through?

Yes, and this is the most common way a king tide causes harm in Marin. A few inches of salt water hides the edge of the pavement, potholes, curbs and open storm drains. Cars stall, and a stalled car in salt water is often a write-off.

Do not drive through standing water, even if it looks shallow.

Low spots on Highway 1 near Tam Junction, the Manzanita park and ride lot, Miller Avenue in Mill Valley and Gate 5 Road in Sausalito all take water during the biggest tides. Caltrans and the county sometimes close lots and shoulder parking before a big tide for exactly that reason.

Why salt water is worse than rainwater

Salt water conducts electricity and eats metal. It gets into brake lines, wheel bearings, wiring looms and the connectors under modern cars, and the damage often shows up weeks later. If you do drive or park in it, rinse the underbody with fresh water as soon as you can.

How High Does a King Tide Actually Get?

A king tide is a spring tide that lands near lunar perigee, when the moon is closest to Earth. NOAA calls these perigean spring tides and says they can run more than a foot higher than other spring tides. On a shoreline built on filled marsh, a foot decides whether the water stops at the curb or crosses the road.

To judge the risk yourself, read the predicted height, not the label. Our guide on how to read a tide chart explains what the numbers mean, and spring and neap tides covers the monthly cycle these peaks come from. Then remember that the chart leaves out wind, rain and storm surge.

Surf on Top of a King Tide

On the outer coast the tide is only half the story. Winter swell arrives on top of the high water, so waves break farther up the beach than the tide line suggests and the strip of dry sand you would normally walk on disappears.

That is when sneaker waves get people. A single wave runs much higher than the ones before it, knocks you down in knee-deep water, and drags you back down the slope. Cold water and a strong backwash do the rest.

Big driftwood logs are the other coastal hazard. A log that looks like furniture can be rolled by one wave and weighs more than you do. Stinson Beach takes the worst of this combination in Marin, where storm surf on a very high tide has reached structures behind the beach.

Can the Tide Cut You Off?

Yes, and it works in both directions. King tide days also bring some of the lowest low tides of the year, which tempts people far out onto reefs and mudflats. Those are the trips where the water comes back behind you. Duxbury Reef and the bay-side flats both drain and refill around rocks and channels, so read our minus tides guide before you go out and leave while the tide is still dropping.

What to Avoid During a King Tide

Driving or walking through standing salt water on a road or path.
Parking in low shoreline lots, especially the hour before the peak.
Standing on jetties, rocks, seawalls or breakwaters with surf running.
Turning your back on the ocean to take a photo.
Walking out on reef or mudflat without a clear, dry way back.
Going out at night, when water on the road looks like wet pavement.

Who Needs to Be Most Careful

Drivers who commute through Tam Junction, Marin City, Lucky Drive or the Canal area in San Rafael, because the water arrives on a schedule and the detours fill up fast.

Photographers and dog walkers are next. Both groups end up closer to the waterline than they planned, one looking through a viewfinder and the other following an animal that has no sense of surf.

Check Conditions Before You Go

Look at the shoreline before you drive to it. The Marin webcams show what the water is doing right now, which is better than any prediction once a storm is involved. If you want a heads-up before the next big one, sign up for tide alerts and plan your trip around the hour either side of the peak.

Where to Look Next

For the specific roads, lots and neighborhoods that go under, and how high the water has to get before they do, open the flooding page. It maps Marin’s tidal flooding spots so you can see whether the next king tide reaches the route you were planning to take.

Start here: Marin tidal flooding.

King Tide Dangers Questions

Are king tides dangerous to people?

For most people a king tide is safe to watch from high, dry ground. The hazards are driving into standing salt water, standing on rocks or seawalls where surf can reach you, and walking out on a flat or trail that the rising tide then covers. The water itself rises slowly, so the danger comes from where you choose to stand or drive.

Do king tides cause major flooding in Marin County?

King tides alone flood low roads, parking lots and paths on the bay side for an hour or two around the peak. Major flooding happens when a king tide lands with heavy rain, storm surge or big surf. Tide tables only cover the pull of the moon and sun, so the real water level can run well above the prediction.

Can a king tide flood my car?

Yes. Low lots and road shoulders near the shoreline take water during the biggest tides, and a car parked there can sit in salt water for an hour or more. Salt water damages brake lines, wiring and electronics, and insurers often write off flooded cars. Park uphill and away from the shore, then walk in.

Is it safe to walk on the beach during a king tide?

Only with room to retreat. A king tide carries surf much higher up the sand than usual, so the dry buffer shrinks and waves can reach driftwood logs, rocks and the base of bluffs. Keep well back from the waterline, never turn your back on the ocean, and stay off jetties, rocks and seawalls.

How much higher is a king tide than a normal high tide?

A king tide is a perigean spring tide, which NOAA says can run more than a foot higher than other spring tides. On the Marin shoreline that foot is often the difference between water at the edge of the pavement and water across it, because many roads and lots sit just above the usual high tide line.