Back-to-back Kona Low systems in mid-to-late March 2026 delivered catastrophic rainfall across the Hawaiian islands, triggering the worst flooding the state has experienced in more than 20 years. Oʻahu's North Shore — world-renowned for big-wave surfing — was submerged under muddy floodwaters that lifted homes, swallowed vehicles, and forced the evacuation of thousands. A 120-year-old earthen dam came dangerously close to failure. Damage estimates exceed $1 billion.
Two subtropical low-pressure systems known as Kona Lows struck the Hawaiian islands in rapid succession during March 2026. These systems — characterised by southerly and southwesterly winds drawing moisture-laden tropical air over the islands — produced prolonged, torrential rainfall that overwhelmed drainage infrastructure and saturated volcanic soils across all five major islands.
The first system arrived around March 13–15, delivering 5 to 10 inches of rain statewide, with localised totals exceeding 30 inches. Weather stations in Honolulu, Hilo, Līhue, and Kahului all broke daily rainfall records. The ground was already saturated when the second, more destructive system hit on March 17–20, dumping an additional 8 to 12 inches on Oʻahu's North Shore in a single overnight period.
The result was catastrophic flash flooding concentrated on Oʻahu's North Shore communities of Haleʻiwa, Waialua, and Mokulēʻia. Raging floodwaters pushed homes off their foundations, submerged roads and vehicles, and cut off entire communities from emergency access. Wind gusts between 60 and 100 mph accompanied the deluge, downing power infrastructure across the islands.
One of the most alarming dimensions of this disaster was the near-failure of the Wahiawā Dam, a 120-year-old earthen dam located approximately 28 km northwest of Honolulu. Built in 1906 to support sugar production for the Waialua Agricultural Company — later acquired by Dole Food Company — the 660-foot dam holds up to 9,200 acre-feet of water.
On the morning of March 20, water levels in the reservoir reached 85 feet, less than 3 feet below the crest. Water poured over the spillway at 1,500 gallons per second. Emergency officials issued an imminent failure notification, warning that a breach would send a wall of water cascading through Waialua and Haleʻiwa, placing 4,000–5,000 people in the direct hazard zone.
The state has classified Wahiawā Dam as "high hazard potential", meaning failure would likely cause loss of life. Dole has received four notices of deficiency since 2009 and was fined $20,000 in 2021 for failing to address safety issues. A 1978 Army Corps of Engineers report first flagged structural concerns — nearly 50 years of deferred maintenance.
The dam previously collapsed in 1921 and was reconstructed. The state regulates 132 dams across Hawaiʻi, most built as irrigation infrastructure for the now-defunct sugar cane industry.
By late afternoon on March 20, water levels receded to 82.6 feet and the evacuation order was lifted. Dole confirmed the dam remained structurally sound. However, the near-miss catalysed political action: the state DLNR board moved to authorise a government takeover of the reservoir to begin critical safety upgrades.
Oʻahu's North Shore sustained the most severe damage. Muddy floodwaters smothered communities across Haleʻiwa, Waialua, and Mokulēʻia. Hundreds of homes were damaged — many pushed off foundations — though a full assessment remains ongoing. Both main access roads (Kamehameha Highway and Kaukonahua Road) were rendered impassable. Landslides were reported across steep terrain. Residential areas of Honolulu also experienced substantial flooding. Up to 115,000 residents faced power outages.
On Maui — still recovering from the devastating 2023 Lahaina wildfire — authorities upgraded evacuation advisories to warnings for parts of Lahaina as retention basins neared capacity. Flooding cut off access to some underserved communities on Maui and Molokaʻi. The Kula hospital sustained damage.
Properties in Kaʻū and South Kona were flooded during the first storm. Several schools sustained damage across the Big Island. Statewide agricultural losses are mounting, with the Hawaiʻi Farmers Union Foundation estimating farm damage exceeding $15 million. Governor Josh Green declared the total cost could exceed $1 billion across public and private sectors, affecting airports, schools, roads, homes, and hospitals.
A Kona Low is a slow-moving, subtropical low-pressure system that forms near the Hawaiian islands, typically during winter months. Unlike trade wind weather patterns, Kona Lows bring southerly or southwesterly winds that siphon warm, moisture-laden air from the tropics. When these systems stall over the islands, they can generate prolonged, intense rainfall far exceeding normal precipitation.
The March 2026 event was exceptional because two Kona Low systems struck within a single week, leaving no time for soils to drain between events. Hawaiʻi's volcanic soils — rich in iron and aluminium oxide — become rapidly saturated, drastically reducing infiltration capacity and converting nearly all subsequent rainfall into surface runoff.
NASA satellite imagery captured from March 14 revealed massive sediment plumes discolouring coastal waters around Kaiaka Bay, as iron-rich volcanic soil was stripped from hillsides and deposited into the ocean. The agency activated its Disasters Response Coordination System to support the Hawaiʻi Emergency Management Agency.
Climate scientists note that the intensity and frequency of heavy rainfall events in Hawaiʻi have increased in line with human-caused global warming. Warmer ocean temperatures provide more moisture to weather systems, while shifts in atmospheric circulation patterns can cause storm systems to stall over the islands for extended periods. Governor Green described the flooding as the state's worst since 2004, when homes and a University of Hawaiʻi library were swamped in a similar event.
Emergency response involved multi-agency coordination across state and federal levels. The Hawaiʻi National Guard was activated alongside the Honolulu Fire Department, US Coast Guard, and county emergency services. Five emergency shelters were opened across Central and North Shore Oʻahu, including at Waialua High School, Wahiawā District Park, and Leilehua High School — all accepting pets.
Recovery resources deployed as of late March include:
Office of Hawaiian Affairs (OHA): $3.96 million in disaster aid for Native Hawaiian households, including $410,000 in direct disaster grants and $250,000 in home repair grants ($10K–$20K per household).
State Department of Agriculture: One-time $1,500 emergency grants for immediate farm recovery, plus emergency loans up to $100,000 at 3% interest. Application deadline March 27 for priority funding.
Hawaiian Electric: Crews restored power to Waialua by March 23, with ongoing work to reconnect remaining 2,000+ affected customers.
FEMA: Flood mapping and damage assessment underway via Esri.
Statewide helpline: Dial 2-1-1 or visit auw211.org for housing, food, clothing, supplies, and transportation resources.
The March 2026 Hawaiʻi floods expose a convergence of climate risk and infrastructure vulnerability that extends well beyond the islands. The Wahiawā Dam near-failure is a stark reminder that ageing water infrastructure across the United States — much of it built in the early 20th century for agricultural purposes that no longer exist — remains critically underfunded and under-maintained. Hawaiʻi alone regulates 132 such dams, most inherited from the defunct sugar cane industry.
For Maui communities still recovering from the 2023 Lahaina wildfire, this compound disaster underscores how climate-related hazards are no longer isolated events but interconnected stressors on resilience. The back-to-back Kona Low pattern — two major systems in rapid succession — is exactly the kind of clustering behaviour climate models predict will intensify as ocean temperatures continue to rise.
Remarkably, no deaths were reported during this event — a testament to the effectiveness of early warning systems, rapid emergency response, and community preparedness. However, the $1 billion+ damage toll and the scale of displacement highlight the growing economic burden of extreme weather on island communities.