Hawaiʻi Reels From Back-to-Back Kona Lows as Flood Losses Near $1 Billion and Wahiawā Dam Spurs State Takeover

The first alerts hit phones on Oʻahu’s North Shore before dawn on March 20.

“LEAVE NOW,” the message warned residents downstream of Wahiawā Dam. After more than a week of pounding rain, water behind the 120-year-old structure had swollen to dangerous levels. City officials said the dam was “at risk of imminent failure.” Sirens wailed through Haleʻiwa and Waialua as families grabbed what they could and rushed for higher ground in the dark.

The frantic evacuation marked the most harrowing hours in what state officials are calling Hawaiʻi’s worst flooding in more than 20 years — the result of back-to-back Kona low storms that lashed the islands through much of March, triggering hundreds of rescues, damaging or destroying homes from Oʻahu to Maui and pushing statewide losses toward $1 billion.

Two storms, one prolonged emergency

Beginning around March 10, a powerful Kona low parked near the islands and unleashed days of heavy rain and damaging winds. Just as the state began to tally the damage, a second system arrived roughly a week later, dropping intense downpours on already saturated ground. The one-two punch turned familiar streets into rivers, undermined roads and buildings, and came perilously close to a dam disaster that emergency managers had long feared.

“This was not one storm,” Gov. Josh Green said as crews worked to restore power and clear debris. “It was a pair of significant weather events, and together they could ultimately cost the state more than $1 billion in damage to airports, schools, roads, homes and a hospital on Maui.”

A Kona low is a cool-season, subtropical low-pressure system that typically forms west or northwest of Hawaiʻi, bringing southerly winds — “kona” winds — instead of the usual trades. Meteorologists say such systems are behind many of the state’s worst floods. The March events fit that pattern and then some.

From March 10 to 16, the first storm brought what the National Weather Service in Honolulu described as an “intense, multi-day Kona storm.” Deep tropical moisture streamed over the islands, breaking daily rainfall records in Līhuʻe, Honolulu, Kahului and Hilo. Gusts reached around 80 mph on Oʻahu and even higher at elevation on Maui and Hawaiʻi Island. At various points more than 130,000 customers lost power.

Maui hit hard as roads fail and floodwaters surge

On Maui, the impacts were swift and severe. In South Maui, local officials called flooding in Kīhei “unprecedented” as stormwater tore through neighborhoods and along the coast. A condominium building in Kīhei partially collapsed after its foundation was undermined, forcing residents to flee. Sections of South Kīhei Road, a key coastal route lined with homes and hotels, washed out or buckled, undercut by rushing water that poured into the ocean.

The storm also raised alarms in Lahaina, where neighborhoods near the 2023 wildfire burn scar received evacuation warnings. Retention basins above Wahikuli and Leialiʻi swelled, and county officials feared debris-laden runoff could threaten communities still in the early stages of rebuilding after the fires that killed at least 100 people less than three years ago.

“We’re still grappling with the impacts of the Lahaina fire, and now some of the same families are facing evacuations all over again,” Maui County officials said in one briefing. Residents and local aid groups described the emotional strain of repeated disaster alerts and dislocation.

As the first storm slowly moved away, Green signed a series of emergency proclamations extending statewide disaster powers. A Fourth Proclamation on March 19 noted that heavy rains and winds since March 10 had caused “significant damage” to transportation and energy infrastructure, including the H-POWER waste-to-energy facility on Oʻahu. It activated the state’s Major Disaster Fund, authorized deployment of the Hawaiʻi National Guard and temporarily suspended wide sections of state law — from public procurement rules to parts of the environmental review and coastal zone management statutes — to speed repairs.

North Shore inundated; hundreds rescued

Forecasters warned that the danger was not over. A second Kona low developed to the west of the islands around March 18 and 19. While weaker overall, it arrived over soaked hillsides, swollen streams and clogged drainage systems.

On March 20, that second system stalled bands of heavy rain over northern Oʻahu. Local observers reported 5 to 10 inches of rain in about six hours. The National Weather Service issued flash flood warnings for Haleʻiwa and Waialua, warning of “widespread life-threatening flash flooding.”

By midday, muddy water had swamped large stretches of Oʻahu’s famed North Shore. Homes were lifted from foundations in some low-lying spots. Roads into Haleʻiwa were cut off. Honolulu officials said more than 230 people were rescued that day alone, some from rooftops or vehicles, by a combination of local first responders, Hawaiʻi National Guard teams and Coast Guard and Navy helicopters and boats.

To protect workers and infrastructure, Hawaiian Electric cut power to parts of the North Shore as the flooding peaked. More than 2,000 customers were still without electricity days later as crews assessed damaged poles, lines and equipment.

Wahiawā Dam near-miss accelerates long-debated action

Above it all loomed Wahiawā Dam, also known as Lake Wilson, an earthen structure built in 1906 to store irrigation water for sugar cane plantations. State regulators classify the dam as “high hazard” because failure could cause loss of life.

Regulatory records show the Department of Land and Natural Resources has issued multiple notices of deficiency to the dam’s owner, Dole Food Co., since 2009, citing needed safety upgrades. In 2019, the state fined Dole $20,000 for delays in addressing those issues.

As the March 20 rain hammered the watershed uphill from Haleʻiwa, water levels in the reservoir climbed toward the top of the dam. City emergency management officials, citing the risk of “imminent failure,” ordered residents in downstream communities to evacuate immediately.

“For those of us who live below the dam, every big storm brings the same fear,” North Shore resident Kathleen Pahinui said later. “People worry the dam will fail during each substantial rain.”

In the end, engineers said the structure held. Water stopped rising, then slowly receded as inflows eased. There was no breach and no reported loss of life from the incident. Still, the near-miss appears to have forced long-discussed changes.

On March 27, the state Board of Land and Natural Resources voted to take over Wahiawā Dam and associated irrigation lands from Dole, clearing the way for at least $20 million in repairs and spillway upgrades. Officials said the transfer would allow the state to directly control safety improvements at a structure that sits above thousands of people and key agricultural lands.

A third jolt: flash flooding in urban Honolulu

Even as North Shore residents shoveled mud from homes and fields, another part of Oʻahu was caught off guard. On March 23, an intense thunderstorm formed near downtown Honolulu, unleashing a downpour that turned city streets into fast-moving streams.

“I was shocked to see how much flash flooding there was in my area,” said resident Andrew Phomsouvanh, who recorded torrents of water rushing past homes and businesses in an urban neighborhood.

Recovery, federal aid and the climate signal

By late March, preliminary statewide damage estimates from the two storms included hundreds of homes damaged or destroyed on Oʻahu, Maui and Hawaiʻi Island; impacts to airports and highways; damage to a hospital in Kula on Maui; and lingering outages and repairs to electrical and wastewater systems. State and federal officials said the exact toll would take weeks or months to calculate. Green formally asked the White House for a Major Disaster Declaration to unlock federal funding.

For scientists, the March floods reflect a pattern they have been warning about: fewer rainy days overall in Hawaiʻi, but more intense downpours when storms do form. A warmer atmosphere can hold more moisture, increasing the potential for extreme rainfall. Research suggests Kona lows may become less frequent as the climate warms, yet the events that do occur could be stronger, delivering multi-day deluges like those seen this month.

Emergency managers and planners now face difficult questions about rebuilding and risk. Low-lying communities such as Kīhei and Haleʻiwa, and neighborhoods below hillside retention basins in Lahaina, remain among the state’s most desirable places to live and visit. Many of the roads, bridges and drainage systems serving them were designed decades ago, under assumptions that a storm dropping 5 to 10 inches of rain in just a few hours was a rarity.

For residents on Maui and Oʻahu, the March floods were less an abstraction about climate and more a test of survival and endurance. Some who lost homes to flames in 2023 saw water creep into replacement housing in 2026. Others packed into shelters twice in a single week as evacuation orders shifted island to island.

As the last of the floodwaters receded and the emergency proclamations shifted into recovery, the visible signs of the storms were everywhere: mud lines on walls, buckled pavement, sinkholes under coastal roads, and sand piled on decks where waves had carried it inland.

Less visible was the lingering unease, especially in places like Haleʻiwa and Waialua, where the whine of warning sirens in the early hours of March 20 may be hard to forget.

The dam above them is still standing. The state has promised to fix it. And out over the Pacific, another cool-season storm will eventually form.