The devastating milestone was announced on March 20 by Hawaii Gov. Josh Green, who said that damages could exceed $1 billion.

The cause is a type of winter storm called a "Kona Low," which is southerly or southwesterly winds that bring moist air onto the islands. This is the second such storm that Hawaii has faced this month.

Green issued a statement on the morning of March 21, stating that no loss of life had yet been reported, although there were some serious injuries. But the back-to-back storms caused some areas to get between 40 and 50 inches of rain.

The first storm hit between March 10 and March 16 and delivered multiple feet of rain to parts of Kawai, Oahu, Maui, and Hawaii Island, as well as winds gusting 60–75 mph and even higher than 100 mph in some areas.

This second storm was expected to bring at least another 10 inches of rain to Oahu and more than a foot of rain to Maui between March 20 and 23.

Hawaii Emergency Management warned on March 21 that Maui and Oahu could still face dangerous rainbands capable of producing two to four inches per hour throughout the day, along with wind gusts reaching 45 mph.

"The storm will deliver another four to six inches of rain on Oahu throughout this weekend, but it's now moving over to Maui, where we expect somewhere between likely four to eight inches, but as much as 10 to 12 in some areas," the governor said.

He also said that the weather will also move over Molokai and the Big Island.

Flash flood warnings remain in effect for the entire island, which hosts military installations like Pearl Harbor and the state's capital, Honolulu.

The National Weather Service's Honolulu office has reported high flood waters closing and collapsing roadways, cutting off entire communities, and lifting homes off their foundations.

Honolulu mayor Rick Blangiardi said on March 20 that dozens, if not hundreds, of homes have been damaged in the storms, but no official damage assessment has been completed yet.

More than 230 people have been rescued, including 72 children and adults who were airlifted by the National Guard and Honolulu Fire Department from a youth camp retreat on Oahu's west coast.

Ten people have been taken to the hospital to be treated for hypothermia.

More than 5,500 residents along the island's North Shore were ordered to evacuate as the consistent rains threatened to cause the Wahiawa dam to fail, which would send rushing waters into their communities.

As of the morning of March 21, the dam remained intact, and some water levels had dropped. But Green later reported that water levels behind the dam were up to nearly 82 feet; 85 feet is the dam's "threshold of great concern."

Meanwhile, other Hawaiian islands also remain under flood threats through the weekend.

Maui's Emergency Management Agency issued evacuation warnings for parts of the ?Iao Valley in Central Maui and parts of Kihei in South Maui because of a potential flooding threat, and it issued advisories for places in East Moloka'i, East Maui, and Lahaina. The agency clarified that neither warnings nor advisories were mandatory evacuation orders.

The Red Cross also deployed disaster assessment teams to Oahu, Maui, and the Island of Hawaii, and the Federal Emergency Management Agency announced that it was monitoring the situation.

"We are monitoring the severe flooding in Oahu and closely coordinating with [Gov. Josh Green] and [Hawaii Emergency Management Agency] as the state leads rescue and shelter operations," FEMA said on X.

"Our teams on the island are embedded and ready to support if needed to help safeguard lives and communities."