The rain bands of Florence, a large and dangerous hurricane, landed on the North Carolina coast Thursday, plowing closer to shore with ever-increasing vigor.

Through Thursday evening the storm dumped up to a foot of rain, winds gusted over 105 mph and seawater surged ashore along the Outer Banks, washing over roads.

“A storm surge of 10 feet above normal levels was reported by the National Weather Service office in Morehead City, North Carolina, at the Cherry Branch Ferry Terminal on the Neuse River,” the National Hurricane Center reported at 11 p.m. Thursday.

In southeastern North Carolina, rivers began to spill into towns. Large areas of New Bern were underwater.

Thursday marked the beginning of a prolonged assault from wind and water, which — by the time it’s over — is likely to bring devastating damage and flooding to millions of people in the Southeast.

Conditions will deteriorate through Friday morning: Winds will further accelerate, the rain will intensify, rivers will swell, and the angry, agitated ocean will surge ashore.

The storm’s center is expected to make landfall Friday in southeast North Carolina, which will coincide with the most severe effects. Storm surge, the rise in seawater above normally dry land at the coast, could exceed a story high. On top of that, a disastrous amount of rain — 20 inches, possibly even as much as 40 inches in isolated areas — is expected to fall.

The National Weather Service says nearly 5 million people could witness at least 10 inches of rain over the next five days as the slow-moving storm made little headway.

Flooding from both the storm surge and rainfall could be “catastrophic,” the National Hurricane Center warned.

[‘That would not be good.’ Hurricane Florence could linger along coast, but much remains uncertain for those in its path]

This same zone will be hammered by winds gusting up to hurricane force for nearly a day while tropical-storm conditions could linger twice that long. These unforgiving winds will damage homes and buildings, down trees and knock out power.

Even though the storm’s category fell from a 4 to a 2 Wednesday and then to 1 Thursday night, forecasters stressed the category is only an indication of the storm’s peak winds in a very narrow core near the center of the storm. The storm’s size and area affected by hazardous winds have actually expanded, and the threat from storm surge and rain-induced flooding “have not changed,” tweeted Rick Knabb, the Weather Channel’s tropical weather expert and former Hurricane Center director.

Gradually, Friday through the weekend, the massive storm — containing a zone of tropical-storm-force winds nearly 400 miles wide — will drift inland, engulfing much of South Carolina and southern North Carolina. Widespread rainfall amounts could reach 6 to 12 inches, spurring flooding. Some of the storm’s wind and rain could even creep into eastern Georgia.

[A ‘no-brainer’: Climate change has made Hurricane Florence worse]

Enough rain could fall to break North Carolina’s record for a tropical storm — 24 inches — set near Wilmington during Hurricane Floyd in 1999, said Greg Carbin, chief of forecast operations at the Weather Service’s national prediction center.

“Put simply, Florence is a ‘Category 5 #flood threat’,” tweeted the Weather Channel.

Flooding from heavy rains is the second-leading cause of fatalities in tropical storms and hurricanes that make landfall.

The rain threat may not stop in the Carolinas. By early next week, a weakened but soggy Florence may drop rain on already saturated Virginia, West Virginia, Maryland, Washington, D.C., and Pennsylvania. These areas are vulnerable to flooding and downed trees after heavy rains this summer.

Weather

On Thursday evening, the Hurricane Center reported heavy rain bands with hurricane-force winds had arrived over North Carolina’s Outer Banks, while tropical storm conditions buffeted areas to the south.

Between 7 and 11 p.m., several weather stations on the Outer Banks reported sustained hurricane-force winds of at least 74 mph and gusts near or over 100 mph. Just before 9 p.m., a weather station on Cape Lookout, N.C., clocked a sustained wind to 83 mph and gust to 106 mph. Another weather station in Fort Macon, N.C., gusted to 105 mph.

To the south, Wilmington had posted a gust to 63 mph. The violent winds had knocked out power to over 100,000 people in the state.

Offshore wave heights surged to at least 28 feet.

[Track Hurricane Florence]

Social media video showed the seas rising at Hatteras Inlet on the Outer Banks, and already some damage from the surge.

The Hurricane Center reported sea levels “increasing quickly” on the western side of Pamlico Sound, where one gauge reported water heights about 4 feet above normal.

Just inland from the coast, flooding was already beginning along the Neuse River in New Bern. Downstream from New Bern, in the town of Oriental, the river level was 6 feet above normal. Read More: