Behind Isaac, Hurricane Helene is gaining strength, with wind speeds of over 105 miles per hour (170 kilometres per hour) as of Monday afternoon.
Hurricane season is in full swing after forecasters predicted that 2018's stint could be as devastating as 2017 when all is said and done. The storm is already 500 miles wide - meaning a large area will be at risk when it nears land.
Initial predictions didn't quite pan out this year - so far, we've had nine named storms and five hurricanes. To the west, a tropical disturbance has developed over the northwest Caribbean Sea. Hurricane damage can go beyond the coast as heavy rain and strong winds are expected inland.
This next map may give you a better idea of when to first expect to feel the effects of the hurricane.
Hurricane Florence is around 500m north of the Leeward Islands, which includes four Commonwealth nations - Saint Kitts, Nevis, Barbuda and Antigua. Florence "is expected to remain an extremely risky major hurricane through Thursday", the NHC said in a statement.
Hurricane Florence rapidly strengthened into a potentially catastrophic Category 4 storm on Monday as it closed in on North and SC. A high-pressure ridge building to the north and northwest of Florence is expected to steer the hurricane west-north-westward to northwestward toward the southeastern USA coast.More news: Ariana Grande Returns to Social Media With Photo of Mac Miller
South Carolina Governor Henry McMaster said Sunday he was asking President Donald Trump for a federal emergency declaration in anticipation of "significant impacts not only on our state but the entire east coast". Vessels that can't leave port will prepare by a variety of means, from adding mooring and storm lines to dropping anchor and disconnecting shore power cables.
Hurricane Florence is expected to bring potentially catastrophic winds, flooding and storm surge.
Preparations for Florence come as the Atlantic hurricane season hits its peak. "Although Isaac is forecast to begin weakening when it approaches the Lesser Antilles, it is still expected to be at or near hurricane intensity when it reaches the islands". Storms in that part of the ocean usually veer away from the U.S.
The NHC issued a warning Monday morning, explaining when powerful gusts may approach.
"USC Athletics is now monitoring the forecast for Hurricane Florence".
On Sunday, Florence reached sustained winds of at least 74 miles per hour to be classified a hurricane. But forecasters say residents should still beware of the chance for unsafe flooding and wind. Locations that have been directly hit by a category 4 hurricane in the past have been uninhabitable for weeks.