I think how well a person tolerates heat (or cold) is a reflection of their overall health.
I think there might be benefits to real dosing yourself with hot weather riding. Heat shock proteins are produced in response to heat exposure, at the cellular level in humans, animals and even plants. And there are some health benefits they confer, such as possible anti-cancer properties. I think they toughen you up a bit as well.
https://en.wikipedia.org/wiki/Heat_shock_protein
Seems like I get a better workout in the heat too (definitely feels like it) and plenty of free vitamin D.