President Joe Biden has warned people in Florida to evacuate as a "matter of life and death" ahead of category four Hurricane Milton's landfall in the state.
Milton has weakened slightly from a category five, but is still packing ferocious winds of up to 145mph (233km/h) after brushing past the northern edge of Mexico's Yucatan peninsula,BBC reported.
The storm is expected to slam into the heavily populated city of Tampa Bay with full force on Wednesday night, less than two weeks after the state was hit by the devastating Hurricane Helene.
Floridians have been told to prepare for the state's largest evacuation effort in years.
Speaking at the White House on Tuesday, President Biden said the storm could be one of Florida's worst in a century.
"Evacuate now, now, now," he told Florida residents, vowing that the federal government would help the state "before, during and after" the hurricane hits.
Thousands of federal personnel are also being deployed, Biden added.
Governor Ron DeSantis said Florida had prepared dozens of shelters to help house residents left stranded in the storm.
"We have one of the sites that can do 10,000," he said in a news briefing. "Others will do multiple thousands. But these are designed to be a shelter of last resort."
He said on Monday that the storm looked like it was going to be a "monster".
In wake of the storm, the White House said Biden cancelled a planned visit to Germany and Angola in order to oversee preparations for Milton, in addition to ongoing recovery efforts for Hurricane Helene.
The government of the Bahamas has now also issued a tropical storm watch for parts of the island nation, including Grand Bahama Island, the Abacos and Bimini.
Less than two weeks ago Hurricane Helene - the deadliest mainland storm since Katrina in 2005 - pummelled the US south-east, killing at least 225 people. Hundreds more are missing.
At least 14 of those deaths were in Florida, where 51 of 67 counties are now under emergency warnings as Milton approaches.
While the hurricane weakened on Tuesday morning, the National Hurricane Center warned that it could double in size before striking Florida on Wednesday.
"Milton has the potential to be one of the most destructive hurricanes on record for west-central Florida," the update said.
In a mid-morning update on Tuesday, the National Hurricane Center said that sustained winds had reached 150mph, down from 180mph the night before.
Hurricanes are separated into five categories based on their wind speed.
Those reaching category three and higher are considered major hurricanes because of their potential for significant loss of life and damage, according to the National Weather Service.
The National Hurricane Center has warned that life-threatening storm surges and damaging winds along portions of Florida's west coast were possible from late Tuesday or early Wednesday.
Rainfall totals could reach localised highs of 15in (38cm), and coastal areas could see storm surges of 10-15ft (3-4.5m).
"Use today as your day to finalise and execute the plan that is going to protect you and your family," DeSantis told residents on Tuesday.
