Yes - it's odd. Not sure if it relates to heat but it may be a factor along with others. I live in Manchester, England - and we rarely get high temperatures over here. Our male siberian is still fine, no other concerns other than the occasional fast breathing. He does sometimes pant (for a few seconds) if he's got over excited and has been dashing about chasing a laser or toy. He's off for his annual booster and vet check very soon, I'll mention the comments on this site.