"While some weakening is expected on Thursday, Florence is forecast to be an extremely unsafe major hurricane through landfall", the NHC said.
Florence is a Category 4 hurricane with winds of 130 miles per hour, and is forecast to approach the coastline of the Carolinas by Friday, the National Weather Service said.
As of Tuesday, about 1.7 million people in North and SC and Virginia were under warnings to evacuate the coast, and hurricane watches and warnings extended across an area with about 5.4 million residents.
How much rain with North Carolina and SC receive? The storm was about 435 miles southeast of Wilmington, North Carolina and 470 miles east-southeast of Myrtle Beach, South Carolina.
Jeff Byard of the Federal Emergency Management Agency said it was imperative locals heed the evacuation warnings. Similar declarations were made earlier in North and South Carolina, Virginia, Maryland and the District of Columbia.
"Been through it!" Belli said, referring to Hurricane Hugo, which caused widespread damage in SC in 1989.More news: Apple shows off iPhone XS
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"Hurricane Florence is the strongest storm to target the Carolinas and this part of our country in decades". Shutdowns also were possible at two more plants in the path of predicted hurricane-force winds.
Smithfield Foods Inc said it would shut down the world's largest hog-slaughtering facility in Tar Heel, North Carolina, on Thursday and Friday due to the hurricane.
"But as we put the tracker on you can see by tomorrow morning we're still anticipating this will strengthen into the neighbourhood of 150mph".
While the hurricane is projected to hit land early September 15, the effects are already starting to be felt from the massive storm. And then from there, it's going across the area meaning a big flooding threat is in the forecast.
Some airlines will allow you to change your flights for free while waiving fees for baggage and pets or even offering refunds.
Hurricane Helene is heading north to open sea off the coast of the U.S. and now poses no danger to land after the storm hit cooler waters in the Atlantic. Hurricane warnings are issued 36 hours before tropical storm force winds hit the areas.
Some people would rather not deal with the hassle of loading up the auto and driving someplace they would rather not be, said Jay Baker, a retired Florida State University geography professor who studies hurricane evacuation behavior.
Long lines formed at service stations, and some started running out of gas as far west as Raleigh, with bright yellow bags, signs or rags placed over the pumps to show they were out of order.