By 5 p.m. Monday, Florence was centered about 1,170 miles (1,880 kilometers) east-southeast of Cape Fear, North Carolina, and moving west at 13 mph (20 kph).
In anticipation of the winds and water, 1.7 million people living along the coasts of the Carolinas and Virginia were ordered to evacuate ahead of the storm. It's now predicted to make landfall somewhere north of Wilmington, N.C., before its center heads inland toward the cities of Raleigh and Durham.
Coastal North Carolina may receive up to 40 inches (100 centimeters) of rain, the National Hurricane Center said.
McMaster said folks should prepare for a lot of flooding in the Pee Dee area.
"North Carolina is taking Hurricane Florence seriously and you should too", said Governor Cooper. "People are doing a pretty good job now". However, that does not make the hurricane any less frightening.
The US president said he had spoken with governors of the threatened states, adding that the "federal government stands by, ready to assist 24/7". "We certainly understand the need for safety, of course, we just felt that tomorrow, making the decision then, would've been more responsible and accurate". "I want to get them as far away as possible". And if it comes this way, we're going to be in for one - a big storm.
"We're seeing that in every ocean basin except the northern Indian Ocean", says Kossin, possibly because climate change is causing the wind currents that hurricanes ride to slow down.
The National Hurricane Center is offering that warning on Tuesday morning as hurricane watches and storm surge watches were issued for the coasts of North Carolina and SC for the first time. That flooding could be exacerbated by increased wave height from Florence.
Helene was weakening, however, and posed no danger to land, the NHC said, while Isaac could bring heavy rain to Martinique, Dominica and Guadeloupe.
Meanwhile, two other storms were also spinning in the Atlantic. "These tropical storms and hurricanes are very risky".
Winds of tropical storm strength could reach Puerto Rico on Friday morning.
A hurricane watch is in effect for Edisto Beach, SC, to South Santee River, SC, and for north of Duck, NC, to the North Carolina/Virginia border.
The National Hurricane Center says a new report from an Air Force Reserve Unit hurricane hunter aircraft indicates that Hurricane Florence's top sustained winds have decreased slightly to 130 miles per hour (215 kph), with higher gusts.
Forecasters expect the storm to linger over the Carolinas once it makes landfall, dumping rain, National Hurricane Center Director Ken Graham told the Associated Press. "This rainfall may produce life-threatening flash flooding".
American Airlines has issued a travel waiver for passengers using 23 airports located in North and South Carolina, Georgia and Virginia, including the hub of Charlotte, for those travelling between 10 and 19 September.
"Florence is expected to be an extremely risky major hurricane through Thursday (Sept. 13)", said officials.
"That's good news and bad news", he said.
Some strengthening is expected during the next 36 hours, and Florence is expected to be an extremely risky major hurricane through Thursday.
A Category 4 hurricane has winds of 130 to 156 miles per hour on the Saffir-Simpson Scale of Hurricane Intensity. Well-built homes can lose walls and roofs.
Power companies warned residents may be without power for days or weeks.
"I don't think many of us have ever been through a Category 4". At that level, it would still cause "devastating damage", according to the Saffir-Simpson scale.
A warm ocean is the fuel that powers hurricanes, and Florence will be moving over waters where temperatures are peaking near 85 degrees (30 Celsius), he wrote. Tropical Storm Isaac is heading westward toward the central Lesser Antilles, but is a bit weaker, with Guadeloupe, Martinique and Dominica now under tropical storm, not hurricane, warnings.