North Carolina alone is forecast to get 9.6 trillion gallons, enough to cover the Tar Heel state to a depth of about 10 inches (25 centimetres).
The worst of the storm's fury had yet to reach coastal SC, where emergency managers said it was not too late for people to get out. The fear is that during that slow march west, it'll drop torrential rains, flooding low-lying areas and overwhelming rivers.
The center of Florence will approach the coasts of North and SC on Thursday, then move near or over the coast of southern North Carolina and eastern SC on Thursday night and Friday, the NHC added.
Hurricane Florence is at the doorstep of North and SC, and she's not going away anytime soon.
As Hurricane Florence makes landfall in the Carolinas, U.S. President Donald Trump Friday tweeted his support for the Federal Emergency Management Agency (FEMA), first responders and law enforcement, stating that they are doing an "incredible job".
More than 80,000 people were already without power as the storm approached, and more than 12,000 were in shelters.More news: Suspects in Skripal poisoning 'civilians, not criminals' - Putin
It remains a Category 1 hurricane with top sustained winds of 80 miles per hour, but stronger wind gusts have been reported.
"I feel like the dumbest human being who ever walked the face of the earth", he said.
Hurricane Florence made landfall Friday morning just east of Wilmington, North Carolina, where it brought a life-threatening storm surge that pushed water inland for miles, pounding rains and powerful winds that battered buildings in its path.
"We know we're in for a long haul here", Cooper said of predictions that the storm will linger over the area.
The center of the hurricane's eye came ashore at about 7.15am Eastern US time near Wrightsville Beach close to Wilmington, North Carolina..
People walk on a local street as water from Neuse River starts flooding houses upon Hurricane Florence coming ashore in New Bern, North Carolina, U.S., September 13, 2018.More news: Hurricane Florence downgraded to Category 2; still a unsafe storm
The news came more than 10 hours after the storm began punishing the coastal area with sustained hurricane-force winds, the hurricane center said. Hundreds more were rescued elsewhere from rising water.
New Bern, which sits along the Neuse River, has seen massive flooding and damage from the storm, and now civil authorities are urging people to get to high points in their homes to await rescue efforts.
Thousands of people hunkered down in schools, shelters and a coliseum in Winston-Salem.
Craven County public information officer Amber Parker says the storm surge has caused flooding in some downtown New Bern businesses, and Union Park is underwater.
The hurricane was seen as a major test for the Federal Emergency Management Agency, which was heavily criticized as slow and unprepared for Hurricane Maria in Puerto Rico a year ago. Officials said some 1.7 million people in the Carolinas and Virginia were warned to evacuate, but it was unclear how many did. As the recovery from past storms continues in many rural towns, the next storm is about to strike.
While Zone A is a mandatory evacuation zone, a city spokesperson said they would never force anyone to leave.More news: Hurricane Florence has weakened but will still be devastating
"The deepest water will occur along the immediate coast in areas of onshore winds, where the surge will be accompanied by large and destructive waves, " it said.