The winds of Hurricane Florence weakened as the storm prepared to hit the U.S. East Coast, but forecasters warn the storm’s overall size and its ability to push ashore a storm surge while dropping tremendous amounts of rain make it a threat to the lives of those in its path.

People in North Carolina and South Carolina have the daytime hours Thursday to complete their final preparations to ride out or escape the storm.

The National Hurricane Center expects hurricane-force winds to reach the coastline near the border of the two states by late Thursday or early Friday. The forecast track has the storm stalling along the coast throughout Friday and into Saturday.

The slow speed will give Florence time to pound the Carolinas with band after band of heavy rain, causing “catastrophic flash flooding and significant river flooding.”

By the time the storm leaves the region, forecasters expect it to drop 50 to 75 centimeters (19-30 inches) of rain in coastal areas, with some parts capable of receiving up to 100 centimeters (40 inches). Farther inland, rain totals could reach 25 centimeters (10 inches) in the Carolinas, and 15 centimeters (6 inches) in neighboring states.

The other threat for those living along the coast is the wall of water known as storm surge that the hurricane’s winds and forward movement push on shore. That could cause normally dry areas to be flooded by up to 4 meters (13 feet) of water moving inland.

The National Hurricane Center said Florence had maximum sustained winds of about 175 kilometers per hour (108 mph) early Thursday, and that it would maintain about that level until the center of the storm makes landfall.

But because hurricane force winds extend 130 kilometers 80 miles) from the center, people on land will experience sharply deteriorating conditions long before the center reaches the coast.

About 10 million people live in areas that were under either hurricane or tropical storm warnings and watches Thursday.

WATCH: Officials Urge Evacuation Before Unpredictable Hurricane

Leaders of the states in the path of the storm have warned people all week to evacuate the most susceptible areas. The governors of North Carolina, South Carolina, Virginia and Georgia declared emergencies to help speed up government aid efforts.

President Donald Trump said Wednesday protecting lives is his “absolute highest priority.”

“We’ll handle it. We’re ready. We’re able,” he said. “We’re fully prepared. Food, medical, everything you can imagine, we are ready.