Damage could be “disastrous”, the state governor said. Evacuation orders have been issued along the coast.
It’s swept across the Caribbean, with the worst of the damage in Haiti.
At least 22 people have been killed in thousands and Haiti. The storm has compelled the presidential election there to be postponed.
Four people were also killed in the neighbouring Dominican Republic.
As of 09:00 GMT, the storm was strengthening over north-western Bahamas. All sea and air traffic has been stopped and folks urged to move to higher ground as a result of storm surges.
Hurricane Matthew was expected to pass near Grand Bahama Island and “move quite close” to the east shore of the Florida peninsula on Thursday night, the US National Hurricane Center (NHC) said.