(Raleigh, N.C.) (AP) — Millions of Americans are preparing for what could become one of the most catastrophic hurricanes to hit the Eastern Seaboard in decades.

Hurricane Florence is carrying winds of up to 140 mph as a Category 4 storm. It is expected to strengthen and possibly become a Category 5 storm Tuesday before closing in on North or South Carolina on Thursday.

Mandatory evacuations have been issued for parts of South Carolina, North Carolina and Virginia, including the entire coast of South Carolina.

Since reliable record-keeping began more than 150 years ago, North Carolina has been hit by only one Category 4 hurricane: Hazel, with 130 mph winds, in 1954.

Hurricane Florence continues to grow in size and magnitude as it barrels toward the U.S. East Coast.

The National Hurricane Center said Monday the monster storm will be close to Category 5 strength by Tuesday. A Category 5 storm has the potential to cause catastrophic damage.

“The bottom line is that there is high confidence that Florence will be a large and extremely dangerous hurricane, regardless of its exact intensity,” the hurricane center said. Florence was a Category 4 storm late afternoon Monday.

At 11 p.m. EDT, the storm’s center was located about 465 miles (750 kilometers) south-southeast of Bermuda and about 1,085 miles (1745 kilometers) east-southeast of Cape Fear, North Carolina.

Maximum sustained winds were clocked at 140 mph (220 kph) as it moved west-northwest at 13 mph (20 kph).

Some strengthening is expected during the next 36 hours, and Florence is expected to be an extremely dangerous major hurricane through Thursday.