Originally Posted by
wolfchild
Heat stroke and dehydration are not the same thing.
No, but related.
Dehydration may reduce one's body's natural cooling. And, of course, sweating and lack of fluid replacement can lead to dehydration.
I will say that with proper hydration, a reasonably fit cyclist seems to be able to maintain body temperature up into the mid 90's. Maybe even over 100° weather. Probably in a large part because riding leads to air movement which helps with evaporation. That is, if one is properly hydrated.