Florence now has maximum sustained winds of 115mph, and gusts to 140mph according to the National Hurricane Center.
This makes Florence a CAT 3, major hurricane, and further strengthening is forecast.
Florence is likely to be a direct threat to the U.S. East Coast late this week.
Hurricane Florence has its sights set on North and South Carolina, and if it hits as hard as predicted, the storm will be the most powerful to pound the area in three decades, CNN meteorologist Chad Myers said Monday.
"This storm gets stronger and stronger" and is on its way to a head-on impact on the Carolinas later this week, Myers said.
Water up to 15 feet high will strike the coast, and rainfall inland over the next four to five days could reach 20 inches in some locations, he said.