The recent cold snap which sent the Miami area's temperatures down into the 40's was not in any way unprecedented. It happens every decade or so. But it was the first such cold snap since the Great Iguana Population Explosion.
No, iguanas are not native to Florida. Like Burmese pythons and lion fish, they're an invasive species, descendants of pets who either escaped or were released into the wild by their owners. When they began falling from trees last week, they should have been barbecued instead of rescued. What South Florida needs is a few good iguana recipes.