By 11 p.m. Sunday, Florence was moving across the Atlantic Ocean at about 7 miles per hour, and it was almost a Category 2 hurricane, with peak winds of 90 miles per hour.
Meanwhile, the two other tropical storms in the Atlantic - Florence and Helen - are expected to become hurricanes today.
The National Hurricane Center in Miami said Florence is expected to become a major hurricane Monday and remain extremely risky and powerful as it nears the U.S. Atlantic coast on Thursday.
Only ten hurricane have made landfall on the Southeast coast since 1851, and if Florence hits North Carolina as a Category 4 it will be the strongest storm to ever come ashore that far north.
The Miami-based center says Florence is gaining strength and is expected to become a major hurricane Monday and keep that status as a powerful and extremely unsafe storm until Thursday.
Met Service said neither of the storms are a threat to Jamaica. The governors of North and SC and Virginia declared states of emergency far ahead of the storm to get ready.
Isaac was about 1,305 miles (2,100 km) east of the Windward Islands on Sunday with maximum sustained winds of 75 mph (120 km/h), the NHC said.
Forecasters urged residents from SC to the mid-Atlantic to get ready - and not just for a possible direct blow against the coast.
Hurricanes reaching Category 3 and higher are considered major hurricanes due to their potential in causing a significant loss of life and damage.
Sunday evening, red flags were up to warn people to stay out of the water, but many surfers were still seen trying to catch a wave. People rushed to get emergency kits ready, map out escape routes and fill sandbags and secure their homes.
The Miami-based center said that it was still too early to predict the hurricane's exact path but that a huge coastal area from SC to the mid-Atlantic region should prepare for a major strike late in the week.
Cooper said the decision to put evacuation orders in place will be left up to local officials, who best know their communities and residents, but predicted that evacuation orders will likely be issued along the coast in the coming days. The state's emergency management agency said it is "preparing for the possibility of a large-scale disaster".
In Jacksonville, North Carolina, about 20 miles (32 kilometres) from the coast, some residents picked up hurricane supplies during their normal weekend shopping, The Daily News reported.
A voluntary evacuation encourages students to leave for a safer location, but it does not require them to leave, say officials.
The Navy planned to send ships from the Hampton Roads area of Virginia out to sea.
Carnival Horizon which is the newest Carnival Cruise Ship has now canceled its scheduled port of call in Puerto Rico due to Florence which is now a category 1 Hurricane.