According to an 11 a.m. update from the National Hurricane Center, Hurricane Florence's maximum sustained winds have intensified to 75 miles per hour.
Florence is moving toward the west near 6 miles per hour, and this general motion is expected to continue today.
The hurricane could reach Category 5 strength, which requires sustained winds of 157 miles per hour or greater.
Several meteorologists said Florence could do what Hurricane Harvey did over Texas, dumping days of rain, although not quite as bad. The storm is expected to approach the southeast U.S. Coast on Thursday.
It stated there is an "increasing risk of life threatening hazards" from storm surge and heavy rainfall but noted it was too early to determine the exact location, timing and magnitude of these impacts.
Knox said residents in North Carolina should begin preparing, "When we put those orders out, when we tell people, 'this is a flood-prone area, ' that you need to find somewhere else to go, don't roll the dice".
"Pretend, assume, presume that a major hurricane is going to hit right smack dab in the middle of South Carolina and is going to go way inshore", South Carolina Gov. Henry McMaster said.
This ridge of high pressure will cause a blocking pattern and steer Florence dangerously close to, or into, the East Coast of the U.S.by midweek.
Florence may make landfall anywhere from New England to the Carolinas as soon as Thursday as a Category 3 or higher hurricane. In the Atlantic there are three named storms, with Florence likely posing a threat to the east coast later this week.
The storm's center was on track to pass between Bermuda and the Bahamas on Wednesday, the NHC said.
Gov. Roy Cooper declared a state of emergency and is urging all North Carolinians to prepare. Hugo in 1989 was the one before that and was a Category 4 at landfall.
Tropical Depression Nine formed 1755 miles east of the Windward Islands Friday. Forecasters predicted it would become a unsafe Category 4 storm before a possible landfall Friday. Strengthening into a tropical storm is forecast this weekend and possibly a hurricane early next week as it approaches the Lesser Antilles.
Florence is still a tropical storm, but is expected to become a hurricane by Sunday, and a major hurricane again on Monday.
The system is expected to move westward over the coming days, and will likely become a tropical storm later Saturday.