Hurricane Florence prompts mandatory evacuations as it nears Category 5 strength

Wilmington, North Carolina (CNN) More than 1 million people on the southern East Coast of the United States faced mandatory evacuation orders as Hurricane Florence neared Category 5 strength Tuesday.

Florence was upgraded twice Monday, from Category 3 to 4, prompting evacuation orders in coastal areas of North Carolina, South Carolina and Virginia. One year after historic storms that ravaged the American Gulf Coast and Puerto Rico last year, officials warned 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.

The size of hurricane-force winds doubled over 12 hours from 30 to 60 miles across, the National Hurricane Center said Monday afternoon. The wind field is expected to keep growing, which will increase the storm surge and inland wind threats, the service said in a statement.

"None of the guidance suggest that Florence has peaked in intensity, and this is supported by a continuation of a low-shear environment, and even warmer waters over he next 36 hours. Thus, the intensity forecast is raised from the previous one, bringing Florence close to Category 5 strength tomorrow," NHS said.

More counties placed under mandatory evacuations

National Guard soldiers are being mobilized in the affected states. President Donald Trump declared an emergency in North Carolina, allowing it to access federal funds.

Six more North Carolina counties were placed under mandatory evacuation Monday night, hours after the first order in Hatteras Island. Certain areas of Brunswick, Currituck, Dare, Hyde, New Hanover, and Onslow counties are affected, and more orders are expected Tuesday.

In South Carolina, mandatory evacuation orders take effect Tuesday at noon in eight counties along the state's 187-mile coastline. Starting then, all roads on I-26 and Route 501 will be directed away from the coast, South Carolina Gov. Henry McMaster said.

"This is a real hurricane we have coming," McMaster said Monday. "We don't want to risk one South Carolina life."