Hermine became the fourth hurricane of the 2016 season around mid-afternoon on Thursday (local time) when its sustained winds reached about 120 km/h.
It is expected to make landfall in Florida around midnight on Thursday night, the first hurricane to hit the state since 2005.
Governor Rick Scott declared a state of emergency for 51 of Florida’s 67 counties, and Georgia governor Nathan Deal declared state of emergency for 56 counties, as residents braced for the dangerous storm.
The last hurricane to make landfall in Florida was Wilma in 2005, the hurricane centre said.
On Thursday afternoon, the NHC extended a tropical storm watch to Sandy Hook, New Jersey.
“This is life threatening. We have not had a hurricane in years,” Governor Scott said.
He added 8000 of the Florida National Guard were prepared to be deployed to deal with the storm.
Mr Scott ordered evacuations in five counties in Florida’s northwest and called for voluntary evacuations in three other coastal counties.
Weather officials predict Hermine will cross Georgia and the Carolinas, and could bring heavy rains along the East Coast over Labour Day Weekend.
The system also poses a risk of tornadoes near the central Florida coast, according to the NHC.
The last hurricane to strike Florida was Wilma in 2005, which made landfall in the US the same year as Hurricane Katrina.