Others in battle-tested Florida were taking no chances. Some had flown out days ago, or braved countless hours of traffic to go north, anywhere north.

The traffic of Irma escapees stretched up to South Carolina, with minivans and pickup trucks packed with people, pets, bedding and even furniture crawling north up Interstate 95. “We left at 4 in the morning; as far as we’ve gone, it’s been bumper to bumper,” said Linda Caldwell as she idled at a gas station in Ridgeland, S.C. The 259-mile journey to that point from her home in Daytona Beach, she said, had taken 12 hours. Her destination was Roanoke, Va.

On Miami Beach, as with every other evacuation zone, mandatory is not really mandatory. People are not forced to leave if they do not want to go. “We let them know there will be no police or fire responding to you when the winds rise above 39 miles per hour,” said Elpido Garcia, a Miami Beach police officer.

In Hollywood, Isaak Kaspler, 80, and his wife, Alexandra, 78, both Holocaust survivors, decided to stay put in their beachside building. They even invited friends over. His daughter pleaded and commanded them to leave but they said no.

“We got shutters here and we’ll close up the shutters,” Mr. Kaspler said. “We got water. We got a radio.” He added, “I feel we’ll be O.K. here.”

In Naples, in the Golden Gate Estates neighborhood, some of the few homeowners who remained were having second thoughts. Russell Spokish said that he had made the decision to stay but that other family members were now starting to panic after hearing news reports.

“I think we’re safe here,” Mr. Spokish said. Referring to forecasts that show Irma moving straight up the state, he added, “It seems if you leave, the hurricane follows you wherever you go.”

At the Betsy Hotel in South Beach, guests were allowed to remain, but they were scared.

“What can we do?” said a woman who gave her name as Sonya and was visiting with her husband from Germany. “In Germany we don’t have situations like this. My sister back home is very scared. She keeps asking, ‘Are you all right? Is the storm there yet?’”