Hawaii Issues Widespread Brown Water Advisories Across Multiple Islands After Kona Low Storm Delivers Damaging Rainfall

Hawaii’s Department of Health has issued brown water advisories spanning four major islands — Kauaʻi, Oʻahu, Maui, and the Big Island — after a powerful Kona Low storm system dumped heavy rainfall across the archipelago. The advisories warn residents and the hundreds of thousands of tourists visiting the islands to avoid contact with floodwaters, coastal runoff, and discolored ocean water due to elevated levels of bacteria, sediment, and potentially hazardous pollutants.

A Kona Low is a distinctive weather phenomenon in the Hawaiian Islands — a slow-moving, upper-level low-pressure system that pulls warm, moisture-laden air from the tropics and drives it northward toward the island chain. Unlike the typical northeast trade wind showers that characterize Hawaii’s normal weather patterns, Kona Lows approach from the south or southwest, often stalling over the islands and delivering prolonged, intense rainfall that can overwhelm drainage infrastructure and saturate the volcanic soil. The name derives from the Hawaiian word “kona,” meaning leeward, as these systems bring rain to the typically drier leeward sides of the islands that are usually shielded from precipitation. When particularly strong Kona Lows develop, they can produce multiple inches of rain per hour, triggering flash floods, landslides, and the kind of massive surface runoff now prompting health warnings across the state.

The brown water advisories represent a well-established public health protocol in Hawaii, but the scope of the current warnings — covering four major islands simultaneously — underscores the severity of this particular storm event. When heavy rains lash the islands, stormwater runoff carries a toxic cocktail of contaminants from land into streams, rivers, and eventually the ocean. These include agricultural chemicals, petroleum products from roadways, construction site sediment, cesspools (Hawaii has an estimated 88,000 cesspools — more than any other U.S. state), and animal fecal matter. The resulting brown plumes that spread along coastlines are not merely unsightly; they contain dangerously elevated levels of bacteria such as Enterococcus and E. coli, which can cause skin rashes, ear infections, gastroenteritis, and in rare cases more serious infections, particularly in individuals with open wounds or compromised immune systems. The Hawaii Department of Health’s Clean Water Branch monitors water quality and typically advises the public to stay out of floodwaters and discolored ocean water for at least 72 hours after rainfall ends, though conditions can persist longer depending on the volume of runoff.

The timing of this storm carries particular significance for Hawaii’s tourism-driven economy. The islands draw visitors year-round, but the winter and early spring months represent a critical high season. Tourism accounts for approximately 21% of Hawaii’s gross state product, generating roughly $20 billion annually. Beach closures and hazardous water conditions directly affect the visitor experience, and repeated storm events can influence future booking decisions. For local communities, the economic ripple effects extend to surf schools, snorkeling tour operators, beachfront restaurants, and rental companies that depend on favorable ocean conditions. At the same time, climate scientists have noted that warming ocean temperatures in the Pacific may be contributing to more intense and unpredictable storm systems affecting the Hawaiian Islands. A 2023 study from the University of Hawaiʻi at Mānoa found that extreme rainfall events in the state have become more frequent over recent decades, consistent with broader global trends in precipitation intensification linked to climate change.

Moving forward, the Hawaii Department of Health will continue to monitor water quality at affected beaches and recreational areas, lifting advisories only when testing confirms bacterial levels have returned to safe thresholds. Emergency management officials are also assessing potential damage to roads, bridges, and coastal infrastructure. Visitors currently on the islands are urged to check the state’s Clean Water Branch website for real-time advisory updates and to heed all posted warning signs at beaches. For the broader Hawaiian community, this latest Kona Low event adds urgency to ongoing debates about infrastructure investment, cesspool conversion timelines, and climate adaptation strategies aimed at protecting both public health and the economic engine of island tourism.