The southern East Coast of the United States is bracing for the arrival of Hurricane Florence as the storm -- already packing winds of up to 140 mph -- neared Category 5 strength Tuesday.

More than 1 million people face mandatory evacuation orders in coastal areas of North Carolina, South Carolina and Virginia, where Florence could begin delivering tropical storm force winds late Wednesday.

One year after major storms ravaged the Gulf Coast and Puerto Rico, officials warned those in Florence's path not to underestimate the threat the storm poses.

Residents boarded up their homes, formed long lines at gas stations and emptied the shelves of hardware stores and supermarkets Monday.
As of 11 p.m. ET Monday, Florence had maximum sustained winds of 140 mph, the National Hurricane Center (NHC) said.
"Some strengthening is expected during the next 36 hours, and Florence is expected to be an extremely dangerous major hurricane through Thursday," the NHC said.

The storm is forecast to strengthen to near Category 5 and "there remains high confidence that Florence will be a large and extremely dangerous hurricane, regardless of its exact intensity," the National Hurricane Center said. A Category 5 storm has sustained winds of 157 mph or more. (CNN)