100°C is somewhat uncomfortable, and it usually indicates that someone is trying to show off. 80 to 90 is much better. (In a sauna.)
I guess it doesn’t happen often, but I saw some upper-90’s temperature in the Portland, Oregon area. It feels relatively mild actually, compared to New England 90’s, I’m pretty sure because it is so dry. The lighter air just carries the heat away, rather than having it stick to you.