Although it is too early to know for certain where Matthew will head after it hits the Greater Antilles, authorities in several southeastern states are making plans should the storm decide to take aim for US soil.
Florida Sen. Marco Rubio echoed Scott's remarks.
Forecasters say the eye of Hurricane Matthew has made landfall near the eastern tip of Cuba.
The governor of SC has ordered the evacuation of more than 1 million people from Wednesday afternoon. "It's approaching Florida with potentially devastating winds", Florida Gov. Rick Scott said at a news conference Tuesday morning. NBC News meteorologist Bill Karins said its path appears to be similar to that of Hurricane Floyd in 1999, which forced the evacuation of 2.6 million people across five states. A considerable amount of uncertainty still surrounds the eventual fate of Matthew, including how it will traverse the islands of Cuba and the Bahamas, how far northwest it will track before making yet another turn to the northeast, and how geographically large the system will become. "Our goal is that you get 100 miles away from the coast".
Meanwhile, Florida and the East Coast prepared for Matthew, a Category 4 hurricane, with more than 1 million people advised to evacuate coastal areas in SC.
The effects of Hurricane Matthew could be felt all the way up the Eastern Seaboard of the U.S. Knabb tweeted a warning on Monday directed to the entire East Coast, urging residents to find out as soon as possible whether or not they are in an evacuation zone.
"As of right now we're looking for Friday night into Saturday being pretty brutal", Haley said.
Hurricane Matthew, with sustained winds around 140 miles per hour, descended on Cuba Tuesday night after crossing over Haiti, where it inflicted heavy damage, reports say.
The department of transportation was already using lane reversals as traffic coming out of coastal cities like Charleston increased. Parts of Georgia, Florida and North Carolina have declared states of emergency.
An evacuation order for Port Canaveral south of Jacksonville was issued on Tuesday. Visitors will evacuate starting at 5 a.m. on Wednesday.
Authorities in Florida have issued hurricane and tropical storm warnings for parts of Florida on Wednesday as Hurricane Matthew, a Category 4 hurricane, moves on after destructively passing through Cuba and the Dominican Republic.
The NWS Miami office also warned in a notice of winds possibly strong enough to damage buildings and snap or uproot trees, along with the potential for power outages.