California’s coastline is facing increased risks of coastal flooding and erosion due to an unusual combination of natural and climatic factors, prompting state and local officials to prepare for potential damage in the coming days. The heightened threat is attributed primarily to an alignment of the Earth, moon, and sun that occurs once every two decades, resulting in exceptionally high “king tides.” These tides coincide with ongoing warm ocean conditions influenced by a developing El Niño event and a persistent marine heat wave, compounding the challenges along the shore.

Between Sunday and Thursday, coastal areas from San Diego to Santa Barbara are expected to experience significant tidal flooding, with the National Weather Service issuing warnings and advisories across Southern California and the Bay Area. San Diego and Orange counties are under a coastal flood warning that anticipates inundation of low-lying homes, businesses, and infrastructure, along with shoreline erosion. Meanwhile, Los Angeles, Ventura, Santa Barbara, and San Luis Obispo counties are under a flood advisory for moderate to significant beach erosion and potential structural damage from seawater intrusion.

Experts note that the unusually high tides this season stem from the near-peak phases of the 18.6-year lunar nodal cycle and the 4.4-year lunar perigee cycle, which affect tide-generating forces. These astronomical influences, combined with sea levels that have risen approximately one foot over the past 125 years due to human-induced climate change, and a warming Eastern Pacific driven by El Niño, have increased the risk profile for coastal flooding.

Unlike earlier floods this year, which were exacerbated by swells from the remnants of hurricanes Marie and Rachel, the current threat is primarily driven by peak tides rather than storm-driven waves. Forecasters caution that these elevated tides could coincide with strong winter storms later this season, potentially worsening impacts.

Areas already vulnerable from prior erosion and flooding events are especially at risk. Long Beach Peninsula suffered major damage earlier this year, including the destruction of its historic boardwalk and damage to homes, while Newport Beach’s Balboa Peninsula has faced persistent flooding and infrastructure stress. Other hard-hit locations include Dana Point, Malibu—where a sinkhole threatens private property—and Carlsbad State Beach, which has seen extensive sand loss forcing closures. Notably, parts of the popular Newport Beach surf spot The Wedge have eroded enough to expose buried infrastructure.

Local response efforts are underway to mitigate anticipated impacts. Newport Beach declared a local emergency and activated its emergency operations center, reinforcing sand berms, preparing pumps and tide valves, and moving thousands of cubic yards of sand to vulnerable beaches. Sandbags are being placed in flood-prone areas, including Balboa Island. Similarly, Long Beach has begun dredging Alamitos Bay to replenish beaches and repair damaged boardwalks. Infrastructure repairs are ongoing along Coast Highway 1 near Crystal Cove, where sand-filled barriers are being installed to stabilize the roadway.

Transportation systems are also adjusting to the forecast. Metrolink announced a suspension of commuter rail service in southern Orange and San Diego counties during the upcoming workweek due to high tide risks. In Northern California, emergency repairs on Highway 37, connecting Marin, Sonoma, Napa, and Solano counties, have prompted an extended closure to raise flood-prone sections by three feet.

Officials emphasize the importance of heeding warnings and taking precautions to protect property and infrastructure from the expected coastal flooding. Scientists warn that similar challenges may arise again during upcoming holiday periods when king tides are predicted to intensify, and they stress that coastal communities should remain vigilant as conditions are anticipated to worsen before improving.