Though Florence has weakened slightly, it’s still a very dangerous storm, and a life-threatening storm surge and rainfall are expected.
Measurements by an Air Force Hurricane Hunter plane indicate that maximum sustained winds have decreased to near 110 mph, with higher gusts.
Forecasters say the storm is likely to remain constant in strength, weakening only after the center of the storm moves inland.
Maryland is not predicted to receive the brunt of the storm.
As of 11 p.m., the storm was centered 280 miles east southeast of Wilmington, N.C., and was moving northwest at 17 mph, and this general motion, accompanied by a gradual decrease in forward speed, was expected to continue through Thursday.
Latest reports have the center of Florence approaching the coasts of North and South Carolina on Thursday. Hurricane-force winds extend outward up to 80 miles from the center, while tropical-storm-force winds extend outward up to 195 miles.
About 10 million people are in the sights of the storm as it zeroes in on the Southeastern coast. Despite the downgrade from Category 4 to Category 2, authorities warned that Florence has an enormous wind field that has been growing larger, raising the risk of the ocean surging on to land.
“Do you want to get hit with a train or do you want to get hit with a cement truck?” said Jeff Byard, an administrator with the Federal Emergency Management Agency.
The National Hurricane Center's best guess was that Florence would blow ashore as early as Friday afternoon around the North Carolina-South Carolina line, then slog its rainy way westward with a potential for catastrophic inland flooding that could swamp homes, businesses and farm fields.
About 5.25 million people live in areas under hurricane warnings or watches, and 4.9 million live in places covered by tropical storm warnings or watches, the National Weather Service said.
Weather Underground meteorology director Jeff Masters said Florence eventually could strike as merely a Category 1 hurricane with winds less than 100 mph, but that's still enough to cause at least $1 billion in damage. Water kills more people in hurricanes than wind, and he said it will still be an extremely dangerous storm for rain and storm surge.
The hurricane center is forecasting the storm to hover near the coast Saturday with winds of around 80 mph before landfall, but with rainfall in the 20 to 30 inches range and up to 13 feet of storm surge.
President Donald Trump both touted the government's readiness and urged people to get out of the way. “Don't play games with it. It's a big one,” he said at the White House.
As of 2 a.m. Thursday, was about 235 miles east southeast of Wilmington, N.C., and about 280 miles east southeast of Myrtle Beach, S.C., moving northwest at 17 mph. The hurricane center said Florence will approach the coast Friday and linger for a while before rolling ashore.
It's unclear exactly how many people fled, but more than 1.7 million people in the Carolinas and Virginia were warned to clear out. Airlines had canceled nearly 1,000 flights and counting. Home Depot and Lowe's activated emergency response centers to get generators, trash bags and bottled water to stores before and after the storm. The two hardware chains said they sent in a total of around 1,100 trucks.
Duke Energy, the nation's No. 2 power company, said Florence could knock out electricity to three-quarters of its 4 million customers in the Carolinas, and outages could last for weeks. Workers are being brought in from the Midwest and Florida to help in the storm's aftermath, it said.
Boarding up his home in Myrtle Beach, S.C., Chris Pennington watched the forecasts and tried to decide when to leave.
“In 12 or 18 hours, they may be saying different things all over again,” he said.
Computer models of exactly what the storm might do varied, adding to the uncertainty. Reacting to the possibility of a more southerly track, Georgia Gov. Nathan Deal declared an emergency but did not immediately order any evacuations.
“I ask all Georgians to join me in praying for the safety of our people and all those in the path of Hurricane Florence,” Deal said.
In Virginia, where about 245,000 residents were ordered to evacuate low-lying areas, officials urged people to remain away from home despite forecast changes showing Florence's path largely missing the state.
Their entire neighborhood evacuated in Wilmington, David and Janelle Garrigus planned to ride out Florence at their daughter's one-bedroom apartment in Charlotte. Unsure of what they might find when they return home, the couple went shopping for a recreational vehicle.
“We're just trying to plan for the future here, not having a house for an extended period of time,” David Garrigus said.
Melody Rawson evacuated her first-floor apartment in Myrtle Beach and arrived at Atlanta Motor Speedway in Hampton, Georgia, to camp for free with three other adults, her disabled son, two dogs and a pet bird.
“We hope to have something left when we get home,” she said. Three other Southern raceways also opened campgrounds to evacuees.
Forecasters worried the storm's damage will be all the worse if it lingers on the coast. The trend is “exceptionally bad news,” said University of Miami hurricane researcher Brian McNoldy, since it “smears a landfall out over hundreds of miles of coastline, most notably the storm surge.”
With South Carolina's beach towns more in the bull's-eye because of the shifting forecast, Ohio vacationers Chris and Nicole Roland put off their departure from North Myrtle Beach to get the maximum amount of time on the sand. Most other beachgoers were long gone.
“It's been really nice,” Nicole Roland said. “Also, a little creepy. You feel like you should have already left.”
The Associated Press contributed to this article.