Frankly depends on how cold they got, and did the fall cause external or internal injuries. Snakes are ectotherms just as iguanas are. Invertebrates, amphibians, and reptiles are all ectotherms. They may be a little less prone to fall out of a tree or depending on the type would even be in a tree, especially when it is freezing.
These animals that are poached out of the tropics, sold as pets, people get tired to the pets and dump them in the wild, are not use to the different climate or environment.