All this cold blooded warm blooded talk is tiring me. The Lore either contradicts itself or the Argonians are an endothermic species that does not like the cold very much. The warm blooded comments make it appear that they are less efficient endotherms or exothermic. However there are many things that make it seem like the Argonians are both Exo and Endothermic. Which is a possibilty with the Hist apparently. Many also assume there is anything related to our worlds biology in this fantasy world called Nirn. It could be as simple as Hist magic. They do not like the cold because they naturally do not live in that environment.
Btw argonians fans. The Hist cant make your entire race super amazingly awesome just like that. They can probably tweak the argos only so much. Though this is just conjecture. Turning and saying the Hist did it for nearly every answer is kind of short sighted. None of us understand how powerful or weak the Hist really are.
My opinion.
Argonians are an exothermic-ish reptilian species that just is not used to the cold. The Warm blood comments may disprove this somewhat though. So far we have small evidence of the Argos being cold blooded AND warm blooded if you choose to use that terminology. Comments by Argonian NPCs saying they are cold and calling other races 'warmbloods' is the evidence for cold blooded and briasts on female argonians, that are there for no reason as far as I can tell, and the fact that the Argonians were not dead is evidence for them being warmblooded. Seriously that Argo would be dead in an hour or so in Solstheim or Bruma if it was cold blooded and outdoors for any long period of time.
Consensus. Warm blooded and does not like the cold. I am sure once we hit the desert areas of Tamriel we will see few Nords there, as its very hot. They can live there they just do not like it very much.