Florida has an invasive species problem, and one of those species is the green iguana. They're not the most impactful and definitely not the ugliest of the invasives, but they do pose serious issues. They damage infrastructure and poop in pools. And every winter, they fall from the trees.
When the temperature drops below a certain point, they go into a frozen stiff state called "torpor." They look dead, but they're just in screensaver mode, and without muscle control they fall from the trees. I've had a plastic dinosaur toy thrown at my head, so I can understand why the National Weather Service issued an alert along with the cold weather forecast.
And it can't be fun for the iguanas. One minute you're freezing your tail off in a tree; next thing you know you're waking up on the sidewalk surrounded by gawkers and you've lost the productive part of your day. The only real winners are the copy editors who get to write headlines like "Florida Forecast: Cloudy with a Chance of Falling Iguanas."