Indeed, humidity matters a lot. Most our saunas here are löyly (in Finnish) saunas, so you get a rollercoaster of dry - humid - dry cycles. Once you get to 100+c and throw a good amount of water on the stones, it can get quite challenging to endure :)

Everybody has their personal preference of course. For me, the sweet spot seems to be a moderately humid sauna at 93c. At that point, the löyly is not too harsh yet but is still hot enough to make you feel alive :)

My steam room (at home) at 116F/47C is close to the upper limit of bearable for me. But that's a lot more humidity than even a humid sauna.