“Which is why you get this phenomenon in South Florida, that it’s raining iguanas,” he said.

“Even if they look dead as a doornail — they’re gray and stiff — as soon as it starts to heat up and they get hit by the sun rays, it’s this rejuvenation,” Mr. Magill said. “The ones that survive that cold streak are basically passing on that gene.”

He believes the iguanas will creep north within a couple of decades, because they will be able to withstand colder climates.

WPLG Local 10, the ABC affiliate, sent a reporter out to observe the process in the wild, or at least on the sidewalk. The correspondent, Parker Branton, captured the slow process as they began to move their arms and legs again, making languid movements as they came back to life.

“You can let the children know at home, these iguanas are going to be O.K.,” he said with a smile.