Hurricane Lane is churning slowly towards Hawaii as schools, government offices and business close and residents stock up on supplies and boarded up homes.
A direct hit could bring the US Pacific island state’s worst storm in a quarter century, forecasters said.
Lane packed sustained winds of up to 230km/h and could dump as much as 50cm of rain that could trigger flash floods and landslides, the National Weather Service said.
Lane – classified as a powerful Category 4 storm on the five-step Saffir-Simpson scale of hurricane strength – was expected to hit the Big Island overnight and slam the island of Maui on Thursday, according to the service.
To the north, Oahu was under a hurricane warning while Kauai remained on hurricane watch meaning it could face similar conditions starting Friday morning.
Governor David Ige urged residents to prepare for the worst by setting aside a 14-day supply of water, food and medicines.
He also announced that all public schools, University of Hawaii campuses and non-essential government offices on the islands of Oahu and Kauai would be closed for at least two days starting on Thursday.
The shelves of a downtown Honolulu Walmart were stripped of items ranging from canned tuna to dog food. Shoppers jostled with one another to get the last boxes of ramen noodles.
City residents used carts to push cases of bottled water and coolers full of ice, after warnings of possible power outages and evacuations.
Cars waited in long lines at gasoline stations in Honolulu and people could be seen pulling small boats from the water ahead of Lane’s expected storm surge.
US President Donald Trump directed FEMA and administration officials to remain in close coordination with the state.
US Navy ships and submarines based in Hawaii were instructed to leave port, a common practice as a hurricane approaches to avoid damage.
As of 7pm (AEST) the storm was centred 380 km south-southwest of Kailua-Kona, the weather service said.
The outer bands of the storm were already dumping 2 to 7cm an hour of rain on parts of the Big Island as the eastern side of the island was under a flash flood warning.
The most powerful storm on record to hit Hawaii was Hurricane Iniki, a Category 4 storm that made landfall on Kauai island on September 11, 1992, according to the National Oceanic and Atmospheric Administration.
It killed six people and damaged or destroyed more than 14,000 homes.