How cold does it need to get before frozen iguanas start falling from trees in South Florida?

It’s that time of year in South Florida: you can smell holiday foods cooking, see families gathering and feel the thump of green iguanas falling from trees. 

Wait, what?

Yes, the invasive green lizard now rampant in South Florida may soon start to chill as temperatures dip with oncoming cold fronts. 

But how cold is too cold for the nonnative reptile? And what should you do if you do find one in a chilly stupor?

We break it down. 

When do iguanas start to freeze?

Firstly, iguanas don’t exactly freeze right away.

Because the animal is cold-blooded, “when temperatures drop below a certain threshold, their metabolism slows down, and they become sluggish,” according to Iguana Control, a company specializing in removing the animal from South Florida properties. 

NBC affiliate WFLA reported in 2023 that according to the Florida Fish and Wildlife Conservation Commission, iguanas slow down when the thermostat dips below 50 degrees. 

They suffer a "cold stun" and may fall from trees when temperatures drop into the 40s and 30s. They could even literally freeze and die at lower temperatures.

But, in 2023, research suggested that Florida’s falling iguana phenomenon could be rarer in the future — both due to climbing global temperatures from unchecked climate change and a shift in cold hardiness in the lizards themselves. That’s right, the big lizards (cue the sci-fi movie music) appear to be adapting.

James Stroud, a postdoctoral research associate at Washington University in St. Louis, found that most of South Florida’s most common lizard species are able to withstand slightly lower temperatures in 2020 than they could even just four years earlier, a drop of about 2 degrees Fahrenheit, according to their paper published in the journal Biology Letters.

Stroud’s study found the magic number for all seven species they looked at was about 44 degrees Fahrenheit. At that point, most South Florida lizards freeze up.

Will iguanas fall from trees during this incoming cold front?

Another cold front arrives Sunday in South Florida, which will bring cooler weather Monday and even colder weather by Tuesday morning.

But the coldest morning looks to be Wednesday, when peak radiational cooling (light winds, clear skies, low humidity) will allow even Miami to dip into the mid-50 degrees.

That's probably not enough to stun an iguana.

But in the suburbs, where it could be five degrees colder, one or two spots may briefly dip into the 40s. That's when, depending on how early you wake up, you may find that it rained iguanas.

What do I do with a frozen iguana?

While the green reptiles may look dead, it’s best to leave them be—and don’t bring them into your home because once the temperatures heat back up, they’ll be revived and start to walk around.

Residents who encounter a stunned iguana can also humanely kill the animal if they’re able to, according to the FWC.