He has also cancelled campaign events Thursday and Friday in anticipation of the storm.
Rain could reach as much as 10 inches elsewhere in North Carolina, Virginia, parts of Maryland and Washington, D.C.
"The combination of storm surge and the tide will cause normally dry areas near the coast to be flooded by rising waters moving inland from the shoreline". That would actually be Florence's storm surge, the Federal Emergency Management Agency said. President Donald Trump tweeted on Monday evening.
Perry says his department has been in contact with power companies and gas pipeline operators.
Long also said the storm was expected to make landfall as a Category 3 or Category 4 hurricane.
Packing maximum sustained winds of 225km/h, the storm ranked as a Category 4 on the five-step Saffir-Simpson hurricane scale and was expected to grow stronger and larger over the next few days, the NHC said. In the six decades since then, many thousands of people have moved to the coast.
If maps of Florence's trajectory are correct, it will become the most powerful storm to strike the Carolinas in almost three decades.
The 8 a.m. forecast changes the storm surge watch for the eastern United States, with the worst impact, a surge of up to 12 feet, expected on a stretch from Cape Fear to Cape Lookout in North Carolina.More news: Gas explosions, fires strike Boston suburbs
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A state of emergency has been declared in both North and SC.
Hurricane Florence has the potential to bring disastrous flooding to areas of the eastern United States already soaked by heavy rain. "This rainfall could produce catastrophic flash flooding and significant river flooding". "We are totally prepared, we're ready, we're as ready as anybody's ever been", Trump told reporters in the Oval Office on Tuesday.
Florence's projected path includes half a dozen nuclear power plants, pits holding coal-ash and other industrial waste, and numerous hog farms that store animal waste in huge lagoons. "We go through a lot of these hurricane scares throughout the years", Wilmington Mayor Bill Saffo said.
All signs pointed to a stronger, slower, wider and wetter hurricane in the days ahead, forecasters said.
Virginia is moving its football game against OH to Nashville, Tennessee due to Hurricane Florence's approach.
The National Hurricane Center in Miami said Helene has maximum sustained winds of 110 miles per hour; however, it's expected to gradually weaken into Tuesday evening and is forecast to become a tropical storm by Thursday.
"Based off recent intensity adjustments, we are now seeing the potential for major Hurricane Florence to achieve a Category 5 intensity prior to landfalling across the Carolinas".
The storm will pick up additional strength as it passes over ocean water with sea surface temperatures of up to 85 degrees, the National Hurricane Center said.
Airlines, including American, Southwest, Delta and JetBlue, have begun letting affected passengers change travel plans without the usual fees. "Even if you've ridden out storms before, this one is different".
NASA astronaut and current International Space Station resident Ricky Arnold was able to capture the sheer breadth of Hurricane Florence, while showcasing Isaac and an outer band of Helene in new photos posted on Twitter Monday. So we should all be even more appreciative than usual this week for their hard work and professionalism.