Sonali Tiwary
Coastal streets across South Florida are flooding this week as a combination of astronomical high tides, sustained onshore winds, and heavy rain overwhelms drainage systems in Miami-Dade and Broward counties. The National Weather Service has issued coastal flood advisories for South Florida, with active warnings in effect through the weekend.
The National Weather Service Miami office has issued coastal flood advisories for Miami-Dade and Broward counties. South Florida's king tide peak is forecast for October 27. The flooding is driven by king tides — exceptionally high tides, sometimes called perigean spring tides, that occur around new or full moons and can be amplified when the moon is also near its closest orbital approach to Earth — combined with sustained northeasterly onshore winds and heavy rain. NOAA tidal prediction stations have recorded above-normal high-tide levels at multiple monitoring points along the South Florida coastline. Low-lying neighborhoods in Miami Beach, Fort Lauderdale, and other coastal communities in Miami-Dade and Broward counties are affected.
Saltwater flooding on city streets does more than inconvenience drivers. Saltwater contact with vehicle undercarriages during repeated drives through flooded intersections can accelerate corrosion. Homeowners in low-lying areas should avoid flood entry into below-grade spaces, where saltwater contact can damage foundations over repeated flood cycles. Stormwater drainage systems in these areas can be blocked by tidal back-pressure, causing floodwaters to linger on streets and in parking garages between rain events.
Why King Tides Cause Street Flooding With No Rain at All
King tides happen when Earth, the moon, and the sun align in a specific orbital geometry that amplifies tidal pull beyond what normal monthly cycles produce. In coastal areas where sea levels have risen over the past several decades, the water height during king tides now exceeds the design capacity of stormwater drainage infrastructure built for earlier baseline conditions.
Most coastal drainage systems work by gravity — stormwater flows downhill through pipes and discharges into the ocean or nearby estuary. When tidal water is already at or above the elevation of the drainage outfall, gravity flow can reverse or stop. Water backs up through storm drains onto streets. The flooding is not from rain falling faster than drains can handle — it is from the ocean pushing back up through the same infrastructure that normally carries runoff out. Sea-level rise and Florida stormwater infrastructure capacity and coastal flooding risk by South Florida county explain the long-term engineering challenge in detail.
That mechanism means flooding can persist on dry, sunny days during king tide peaks. The combination this week of astronomical tides with onshore wind-driven wave action is extending the flooding window beyond the high-tide peak itself, keeping water on streets and in low-lying parking areas for longer stretches between tidal cycles.
What causes king tides to flood Florida coastal streets?
King tides, also called perigean spring tides, are exceptionally high tides that occur around new or full moons. They can be amplified further when the moon is near its closest orbital approach to Earth. Coastal stormwater drains rely on gravity to discharge into the ocean, but when tidal water is already at or above the outfall elevation, drainage can reverse and seawater pushes back onto streets through storm drain openings.
NWS forecasts show South Florida's king tide peak on October 27, with above-normal tidal conditions expected through October 30. South Florida flooding forecast and advisory updates will track the advisory status as conditions change.
