“We are praying and hoping for the best,” she said.

The badly flooded areas were all around town, not isolated to just one spot, said Jameesha Harris, an alderwoman, who heard from constituents whose relatives had fled to their roofs. “Downtown is literally underwater,” she said.

Since a mandatory evacuation was ordered for New Bern earlier in the week, city officials had tried to get word out. They knocked on doors, left fliers and drove the streets broadcasting on fire truck bullhorns. They offered rides. “If you were even afraid that you might flood,” said Jeffrey T. Odham, an alderman who made the rounds, “then you probably could flood this time.”

The state had set up a shelter at a National Guard armory two hours inland, and hundreds had gone. Four local shelters had been set up, as well, for last-minute deciders, and they filled up.

But still, some people remained. They stayed because they were up there in age, on dialysis, because they did not hear of the mandatory evacuation, because they had faith that God would keep them safe, because they loved their homes and did not want to leave, because it had never flooded badly where they lived.

But as Thursday afternoon turned to evening, it had become ever more clear that Hurricane Florence was not going to be like any storm in memory. Surgewaters marched down streets and crept up front porches, knocking on windows and sending people to second floors, then attics, if they had them.

“It was close to dark, I’d say probably 5, 6 o’clock, and these floodwaters were really starting to rise and were rising quickly,” Mr. Odham said.

People lost power all over town. A local television station, surrounded by floodwaters, had to evacuate in minutes, the weatherman walking off the set mid-broadcast. Those who did not get out had been told: If there is no room in the attic, go higher. And some did, clambering up onto the rooftops to wait.