Meteorologist Ryan Maue of weathermodels.com said Florence could dump a staggering 18 trillion gallons (68 trillion liters) of rain over a week on North Carolina, South Carolina, Virginia, Georgia, Tennessee, Kentucky and Maryland.
A North Carolina city says about 70 people have been rescued from a hotel whose structural integrity is being threatened by Hurricane Florence.
With flood waters rising rapidly in many communities, people trapped in homes awaited rescue, while tens of thousands hunkered down in shelters after fleeing their homes as the storm approached.
"The sun rose this morning on an extremely unsafe situation and it's going to get worse", he said at a news conference in Raleigh.
Utility crews worked to restore electricity.
One grocery store in Myrtle Beach, South Carolina, sported a plea for divine intervention - with forecasters warning that the threat of devastation remains high despite the downgrade.
The National Hurricane Center said a gauge in Emerald Isle, North Carolina, reported 6.3 feet (1.92 meters) of inundation.
Forecasters said wind speeds have dropped from a high of 140 miles per hour (225 kph) to 110 miles per hour (175 kph), reducing it from a Category 4 storm to a Category 2, and additional fluctuations and weakening were likely as it swirled toward land.
Hurricane Florence: Carolinas brace for life-threatening storm
More significant weakening was expected over the weekend and into early next week while Florence moves inland, the NHC said . The storm's forward speed had slowed to 6 miles per hour , and forecasters were concerned it might have stalled.
The centre of the hurricane's eye came ashore last night Singapore time near Wrightsville Beach close to Wilmington, North Carolina, with sustained winds of 150kmh, the National Hurricane Centre (NHC) said.
The flooding soon spread into SC, swamping places like North Myrtle Beach, in a resort area known for its white sands and multitude of golf courses. Residents in areas on high alert continue to evacuate.
As of Tuesday, more than 1.7 million people in the Carolinas and Virginia were warned to clear out.
A buoy off the North Carolina coast recorded waves almost 30 feet (9 meters) high as Florence churned toward shore.
The outer bands of the storm were already reaching the coast Thursday, bringing tropical-force winds and rain.
Mr Trump was later briefed in the Oval Office in front of TV cameras by Brock Long, head of the Federal Emergency Management Agency (Fema).
And while the intensity of Florence's winds - still in the 90 miles per hour range - have diminished enough to turn it into a Category 1, the storm has grown in size as it crawls off the coast at a plodding 6 miles per hour.
A mother and baby were killed when a tree fell on a house, according to a tweet from Wilmington police.
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Perhaps opposing teams are being more careful defending Delle Donne, because when she does get to the line, she's automatic. Stewart, the MVP, and Loyd carried the scoring for much of the season, combining for almost 40 points per game.
Areas along the coast from Cape Fear to Cape Lookout, NC, including the Neuse, Pamlico, Pungo and Bay rivers may experience storm surges from 9 to 13 feet.
The storm has pretty much followed the forecast track through now, but the issue will be Thursday or Friday as it nears the coast and the steering currents collapse.
"But I'm staying", she said.
A surge is also likely along portions of the SC coast.
This is the third time SC has had to cancel a game due to weather in the last four years.
DeWine's campaign spokesman Josh Eck says the campaign wasn't targeting potential hurricane viewership.
"Our friend behind our old house, they have gators swimming in the water". Trump plans a visit to the region next week.
An extremely powerful hurricane is forecast to make landfall in the southern part of the United States later this week.
Canada sees more NAFTA talks this week, much work remains
This won't get resolved in an afternoon", said the source, who declined to be identified given the sensitivity of the situation. The U.S. and Mexico are intent on wrapping up the matter before December 1, when Mexico's new president will be sworn in.