In my case it almost feels like my body's reaction to heat has a screwed-up sense of how hot things are. I can't take hot showers, for example, which are objectively not dangerous, because they genuinely feel like they are going to burn me - normal-hot-shower temperature water feels like like a wet hot pan, it's like my cap is just lower. Ambient heat in the air and light doesn't do that in the same way, but it can make walls and stuff feel like that, naturally.

I hadn't thought of it from the overstimulation angle before, though, but now that I think about it I think you're right, that is at least part of why I hate ambient heat and particularly sweating. Thank you for that insight.