Here is a resource that I saw was used in an older thread, though it is about veiled chameleons:
http://www.chameleonnews.com/08FebLong.html
Perhaps some information can be gained over that. You can also check this website:
(link no longer valid)
It suggests that chameleons are one of the species that are genotypically driven, so basically the outside temperatures during incubation don't matter. That is just a theory though, and it doesn't look like it has any proof (yet!)
Hope that helped!