People fill sandbags as a flood control tool in West Miami. (AFP)

Hurricane Dorian roared Saturday towards the Bahamas as the island chain braced for a devastating direct hit, before the monster storm churns up the US coast from Florida towards the Carolinas.

Barreling in from the Atlantic Ocean, the extremely dangerous Category 4 storm is set to hit parts of the northwestern Bahamas hard on Sunday, the US National Hurricane Center (NHC) said in its latest bulletin at 2100 GMT.

Further ahead the NHC said Dorian would “remain a dangerous hurricane through 5 days,” but exactly where — and how hard — it will strike the US coast looked increasingly uncertain after the storm shifted course overnight, apparently sparing Florida the worst.

In Grand Bahama, businesses were boarded up and thousands of people have evacuated the predicted storm path with forecasts of devastating winds, life-threatening surf conditions, and storm surges of up to 15 feet (4.5 meters).

Yasmin Rigby, a resident of the island’s main city Freeport, told AFP “people are moving out of the east and west ends, fearing the worst.”

Shelves in grocery stores were “just about cleared,” Rigby said, and most homes and businesses had been shuttered since Friday.

She said memories of past hurricanes were still fresh, including Wilma in 2005 — a storm of historic dimensions. “It took weeks for water, food and electricity to be back to normal.”

The storm’s leisurely pace of eight miles per hour (13 kph) means it could deposit as much as 25 inches of rain in the northwestern Bahamas.

That, coupled with the storm surge predictions, poses a fearful prospect for many of the islands, some barely feet above sea level.

Still, Rigby — who lives in the central part of the island — was among the Grand Bahamians who said they intended to ride the storm out.

“I’m checking weather reports but will be staying at home,” she said.

“Where I am, it’s not that bad. I will be filling tubs of drinking water tonight to wait it out.”

Currently located about 170 miles east of the Bahamas’ Great Abaco island, Dorian will keep moving slowly westward through the weekend, drawing near the Florida east coast late Monday through Tuesday, the NHC said — but is then forecast to turn northward towards Georgia and the Carolinas.

The NHC has not ruled out Dorian making landfall in Florida, however.

“Uncertainty remains high as any small shifts in the track could substantially change the potential impacts for locations along the Southeast US coast,” the National Weather Center Eastern Region wrote on Twitter.

Supplies at a Walmart in West Miami run low as residents prepare for Hurricane Dorian. (AFP)

Dorian’s current strength, with maximum sustained winds of 150 miles per hour (240 kph) and even more powerful gusts, makes it nearly a Category 5 hurricane — the highest and most damaging level.

In the Bahamas, government offices were closed and people rushed to prepare for a storm they were told could prove catastrophic.

“The price you may pay for not evacuating is your life or other serious physical harm,” Prime Minister Hubert Minnis warned residents in Dorian’s path.

Donald Trump, who canceled a high-profile trip to Warsaw to focus on storm preparations, was “being briefed every hour,” his spokeswoman Stephanie Grisham told reporters who accompanied the president to his Virginia golf course on Saturday.

Trump, who owns properties including the Mar-a-Lago resort in Florida, tweeted that Dorian’s path was “very hard to predict, except that it is one of the biggest and strongest (and really wide) that we have seen in decades. Be safe!”

Given the storm’s uncertain path, coastal Florida residents were not yet under evacuation orders but stocked up on supplies and weighing whether to flee their homes.

While Miami appeared likely to be largely spared, one man picking up sand bags there Saturday, David Duque, 30, noted that “everything could change… I know it could be a scare, but better prepare instead of doing nothing.”

The Florida National Guard said about 2,000 service members had been mobilized, with another 2,000 poised to join them.