Does being in good cardio shape help heat tolerance?

One of the things I've noticed after doing a lot of cardio work for the last few months is that even exercising a lot in almost 100 degree F weather doesn't even seem to bother me. I really don't feel uncomfortable at all as long as I drink plenty of water.

Why does being in good cardio shape help the body adjust to the heat?

How come that Minnesota Vikings football player died? Don't they drink plenty of water and do a lot of cardio work too?

Fairly obvious really: the heart, lungs, and general circulation are healthier and therefore able to remove heat more efficiently.

This can actually work against an athlete in the opposite situation of hypothermia. For example, stranded in cold water, the athlete will be the first to go and the fat guy the last.

Everyone has their limits. Athletes can and do die of heat stroke.