The poorly organized, 45-mph storm is not expected to strengthen but should maintain its tropical storm strength for the next few days.
While hurricane-force winds can rip the roofs off houses, it is the water - storm surge, inland flooding, surf and drowning at sea - that kills almost 9 out of 10 people in hurricanes like Florence. The forecast track has the storm moving slowly along the coast throughout Friday and into Saturday.
Weather Underground meteorology director Jeff Masters said Florence eventually could strike as merely a Category 1 hurricane with winds less than 100 miles per hour (160 kph), but that's still enough to cause at least $1 billion in damage.
Terrifying as the situation is (I am regularly checking on my folks, who abandoned Charleston for the highlands of North Carolina), there is a silver lining. "For these airports along the coast, like Charleston and Myrtle Beach, the wind and the tidal surge will be the biggest issues".
Its surge could cover all but a sliver of the Carolina coast under as much as 3.4 metres of ocean water, and days of downpours could unload more than 900mm of rain, triggering severe flooding.
Businesses and homes in the storm's path were boarded up and thousands of people had moved to emergency shelters, officials said.
Hurricane Florence is not expected to make landfall until Friday morning but residents in coastal areas are already losing power as gusts lash the eastern edge of North Carolina.
Fears about Hurricane Florence spread south on Wednesday, with Georgia declaring a state of emergency after officials in the Carolinas urged people to evacuate the coast ahead of the storm's expected pounding winds and rain-driven floods. Tropical Storm Isaac is forecast to approach the Lesser Antilles Islands on Thursday.
He added: 'The waves and the wind this storm may bring is nothing like you've ever seen. "The larger and the slower the storm is, the greater the threat and the impact - and we have that".
But then the screen behind Navarro becomes the storm surge itself, and, well, you just have to watch the whole thing.
There are generally three components to a hurricane; strong winds, storm surge and heavy rain. Restoring power to all customers could take weeks, the utility warned.
Florence is the most risky of three tropical systems in the Atlantic. The forecasters say the slow speed will give Florence time to pound the Carolinas with bands of heavy rain. "We're forecasting 30 inches of rainfall". "Significant river flooding is expected as a result of excessive rainfall across area hydrologic basins".
"This is a life-threatening situation".
Images captured by Associated Press journalists show the angst of evacuation and solitary beachgoers finding moments of calm before the storm. "The combination of a unsafe storm surge and the tide will cause normally dry areas near the coast to be flooded by rising waters moving inland from the shoreline".
U.S. television networks said 7pm to 7am curfews had been put in place in several towns surrounding Myrtle Beach.
That was a bad idea, said Avair Vereen, a local nurse who had sought safety in the shelter with her seven children.