Thus far, 1.7 million people have been required to leave their homes in the coastal areas of North Carolina, South Carolina, and Virginia, and millions of homes have been put under official watch or warnings for extreme weather conditions.
The center of Florence, no longer classified as a major hurricane but still posing a grave threat to life and property, is expected to strike North Carolina's southern coast on Friday, then drift southwest along the shoreline before moving inland on Saturday, according to the National Hurricane Center (NHC) in Miami.
Wilmington, North Carolina, just north of where the hurricane is expected to come ashore, was sunny around midday on Wednesday as the town appeared to be emptying. The child's father was injured and taken to a hospital.
In Washington, North Carolina, the wind-swept Pamlico River burst its banks and flooded entire neighbourhoods.
A fourth person was killed while plugging in a generator in Lenoir County, north of Wilmington, WITN-TV reported.
A spokeswoman for Love's Travel Stops says demand for gasoline has doubled at numerous company's truck-stop locations in the path of Hurricane Florence.
President Donald Trump said his administration was "as ready as anybody has ever been" to respond to the storm.
"Hurricane Florence is powerful, slow and relentless", North Carolina governor Roy Cooper said.
Hurricane Florence: Storm downgraded but threat remains
Police patrol past boarded up shops along the boardwalk in Myrtle Beach, South Carolina ahead of Hurricane Florence's arrival. The National Guard is on standby in North Carolina, South Carolina and Virginia to deal with emergencies as they arise.
"This is going to be a Mike Tyson punch to the Carolina coastline".
Authorities in New Bern, a town of about 30,000 people that dates to the early 18th century, said more than 100 people had to be rescued from floods. "We are stuck in the attic".
"The deepest water will occur along the immediate coast in areas of onshore winds, where the surge will be accompanied by large and destructive waves, " it said.
In Jacksonville, North Carolina, more than 60 people were evacuated from a hotel after part of the roof collapsed, city officials said.
North Carolina alone is forecast to get 9.6 trillion gallons enough to cover the Tar Heel state to a depth of about 10 inches. We know it has forced the cancellation of almost 1,800 flights, with more to come, and that it has already caused serious flooding in coastal areas.
The eye of the storm reached Wrightsville Beach, several miles east of Wilmington, around 7:15 eastern time, with estimated maximum winds of 90 mph. Florence weakened on Tuesday morning when the storm went through eyewall replacement. He says that "over the years the state government and the federal government have become very coordinated in their ability to manage the pre-deployment of assets (and) the response to the citizens of those states, and we will soon be into the recovery".
Storm surge, the massive mound of water that builds up and comes ashore during a hurricane, is often the deadliest and most destructive threat from the storms. Forecasters said Florence is expected to blow ashore late Thursday or early Friday, even as President Donald Trump has declared states of emergency for North and SC and Virginia, opening the way for federal aid.