It currently has maximum sustained winds of nearly 130 mph (215 km/h) according to the US National Oceanic and Atmospheric Administration (NOAA). Hurricane Dorian is expected to hit Florida either late on Monday or Tuesday.
States of emergency have been declared for Florida and North Carolina, as well as 12 counties in Georgia.
South Carolina is also on high alert, while the Caribbean state of Barbados has a hurricane warning in place.
It has been estimated that 20 million Americans could be hit by the storm.
Mandatory evacuations will take place on Sunday for Brevard County, which includes the Kennedy Space Centre, and Martin County in Florida.
President Trump is due to attend a hurricane briefing in Washington on Sunday at 12:30pm Eastern Time (5:30pm British Summer Time).
He also spoke to Florida Senators Rick Scott and Marco Rubio on Friday.
The governor of New York has sent a team of 26 emergency workers to support colleagues in Florida.
Governor Andrew Cuomo commented: “As Hurricane Dorian continues to gather strength on its path toward the US, we are preparing for every possible scenario and stand ready to assist Florida and any other community impacted by the storm.
READ MORE: Hurricane Dorian – Donald Trump properties could suffer
Walt Disney World, Florida’s biggest tourist attraction, is still open but some events have been cancelled.
The site is the most visited resort in the world, with over 52 million people attending each year.
In a statement Walt Disney World Communications said: “Walt Disney World Resort is operating under normal conditions.
“We are closely monitoring the path of the projected weather, as nothing is more important than the safety of our guests and Cast Members.
“We are taking precautions including canceling weekend sporting events and closing Disney’s Blizzard Beach Water Park on Sunday.”
Orlando International Airport will cease commercial operations on Sunday.
The announcement was made by Phil Brown, the Greater Orlando Aviation Authority CEO.
In a statement he said: “Hurricane Dorian has strengthened and slowed.
“We don’t know exactly where Dorian is going but we do know that it will have a significant impact on the entire state of Florida.
“So in order to allow the airport’s 25 thousand employees time to secure their homes and families we feel it is prudent to cease operations in a timely fashion.”