Summary (tl;dr)

Coastal flood warnings are trending as Tropical Storm Rachel approaches Southern California, bringing a "double whammy" of high surf, elevated tides, and coastal inundation exacerbated by an El Niño-driven Kelvin wave and rising sea levels.

Essential Background

Coastal flooding has become increasingly frequent and severe across U.S. coastlines, with human-caused sea level rise accounting for approximately eight out of every ten days with coastal flooding over the past decade (2016-2025). The frequency of coastal flooding has more than tripled since the 2000s, reaching an average of 14 days per year between 2020 and 2025. This year, the recurring El Niño pattern, which periodically warms sea surface temperatures in the eastern Pacific Ocean, has continued to strengthen and is predicted to bring more high tide flooding, particularly to the U.S. West Coast. An additional factor contributing to current flood risks in California is a large, slow-moving Kelvin wave, an oceanic phenomenon that can elevate sea levels by up to a foot.

The Full Story

Currently, "coastal flood warning" is trending due to the immediate threat posed by Tropical Storm Rachel, which is making a rare approach toward the Southern California and Mexico border. This storm system, combined with elevated sea levels from an El Niño-driven Kelvin wave and seasonal high tides, is generating powerful waves, dangerous rip currents, and significant coastal flooding across Southern California. The National Weather Service has issued coastal flood warnings and advisories for various areas, including Los Angeles, Orange, and San Diego counties, with the highest risks projected through the weekend, especially around Sunday morning, when high tides are expected to exceed seven feet. Already, communities like Newport Beach and Long Beach have experienced substantial flooding, with seawater inundating streets, damaging homes, and even crumbling sections of boardwalks.

Why It Matters

This trend is critical because coastal flooding poses serious risks to lives, property, infrastructure, and local economies. The combination of tropical storms, high tides, and climate-change-induced sea level rise can lead to widespread disruption, including road closures, damage to homes and businesses, and threats to essential utilities. Experts emphasize that these extreme sea level events, once rare, are becoming far more common, making it crucial for coastal communities to implement robust preparedness and mitigation strategies. The ongoing events in Southern California serve as a stark reminder of the escalating impacts of climate change and natural climate patterns on vulnerable coastal regions.

Geographic Location

• Long Beach, Los Angeles County, California, United States (coastal flooding, boardwalk damage, beachfront property damage)
• Avalon, Los Angeles County, California, United States (coastal flooding risk)
• Malibu, Los Angeles County, California, United States (coastal flooding risk)
• Newport Beach, Orange County, California, United States (street flooding, local emergency declaration, significant property damage, large waves)
• Laguna Beach, Orange County, California, United States (flooding reported)
• San Onofre State Beach, Orange County/San Diego County Boundary, California, United States (damage to access road)
• San Diego County, California, United States (Tropical Storm Watch, coastal flooding, heavy rain, dangerous surf)
• Santa Cruz County, California, United States (coastal flood advisory, 16-foot waves, dangerous surf)
• Corte Madera, Marin County, California, United States (king tide flooding in January 2026)
• Ventura County, California, United States (coastal flood and high surf advisories)