MYRTLE BEACH, S.C.  — Hurricane Florence put a corridor of more than 10 million people in the crosshairs Wednesday as the monster storm closed in on the Carolinas, uncertainty over its projected path spreading worry across a widening swath of the Southeast.

Faced with new forecasts that showed a more southerly threat, Georgia’s governor joined his counterparts in Virginia and North and South Carolina in declaring a state of emergency, and some residents who had thought they were safely out of range boarded up their homes.

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 push its rainy way westward with a potential for catastrophic inland flooding.

Florence’s winds in the afternoon were down to 120 mph (195 kph) from a high of 140 mph (225 kph), and the Category 4 storm fell to a Category 3, with a further slow weakening expected as the storm nears the coast. But authorities warned it will still be an extremely dangerous hurricane.

“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.

Tropical storm-force winds extended 195 miles (315 kilometers) from Florence’s center, and hurricane-force winds reached out 70 miles (110 kilometers).

The National Weather Service said 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.

At the White House, President Donald Trump both touted the government’s readiness and urged people to get out of the way of Florence.

“Don’t play games with it. It’s a big one,” he said.

As of 5 p.m., the storm was centered 385 miles (615 kilometers) southeast of Wilmington, North Carolina, moving northwest at 16 mph (26 kph). The hurricane center said Florence will approach the coast Friday and linger for a while before rolling ashore.