Roughly the size of Tasmania, experts say Hurricane Irma is the most powerful Atlantic Ocean hurricane in history.
Hurricane Irma has already churned across Antigua and Barbuda, the Virgin Islands and Puerto Rico in the Caribbean with a catastrophic mix of fierce winds, surf and rain.
The prime minister of Antigua and Barbuda, Gaston Browne, says it has caused an estimated AU$70 million in damage.
The French island territories of Saint Martin and Saint Barthelemy have also been hit, with French president Emmanuel Macron predicting casualties there.
And now the hurricane, bearing winds of almost 300 kilometres an hour, is heading for the United States on a path predicted to hit the Dominican Republic, Haiti and Cuba first.
With the Dominican Republic expected to be hit later today, officials there have set up thousands of shelters, with space for almost a million people.
The country's executive director of civil defence, General Rafael Antonio Carrasco Paulino, says evacuations have been ordered in specific zones.
"Evacuations have been carried out in San Cristobal. These people have been transferred to family members' homes. We are yet to use any of the 3,262 shelters that are distributed around the whole country, which have a capacity for over 900,000 people."
The heaviest damage is potentially coming in the United States, though, with the state of Florida lying in the current path of the hurricane.
Florida governor Rick Scott has already declared a state of emergency in all 67 of the state's counties.
He has warned residents the hurricane's impact could be greater than that of Hurricane Andrew, which killed 65 people and caused AU$33 billion of damage in 1992.
"Storm surge and extreme winds are the biggest concern right now. The storm is bigger, faster and stronger than Hurricane Andrew. We are being very aggressive in our preparation for this storm, and every Floridian should take this seriously and be aggressive to protect their families."
Heeding the governor's warning, Floridian residents are stocking up on supplies.
Residents of Monroe County, centred around low-lying Key West, are under a mandatory order to evacuate the area.
Packing groceries into her car outside a supermarket, Paula Acosta says the gravity of the situation is becoming apparent.
"The line to get water goes around the whole supermarket. And they only give you two (of) whatever you ask for per person. The lines are crazy. Cashiers ... it's packed, it's full."
Another resident, Denise Perry, says supplies are becoming scarce.
"(I) sent my husband out yesterday to get some supplies. He didn't bring back with a whole lot of stuff, so I had to come back and get some water. The manager just told us that they don't have any water in yet, so I'm going to pick up some other non-perishable items, get prepared for the storm."
United States president Donald Trump's hurricane-response team has already turned part of its attention from Hurricane Harvey's devastation in the state of Texas to Florida.
The recovery in still underway in Texas, with the death toll now confirmed at more than 70 and damage estimated at over AU$225 billion.
