The delta here is your understanding of what a sauna is (or your understanding of the definitions involved), not the reality of what a sauna is.

https://en.wikipedia.org/wiki/Sauna#Modern_saunas

> In a typical Finnish sauna, the temperature of the air, the room, and the benches are above the dew point even when water is thrown on the hot stones and vaporized. Thus, they remain dry. In contrast, the sauna bathers are at about 60–80 °C (140–176 °F), which is below the dew point, so that water is condensed on the bathers' skin. This process releases heat and makes the steam feel hot.

Putting water on hot stones in a sauna does not raise the humidity nearly as much as you think it does.

Sounds like it doesn't have to be wet to be a sauna.

> A sauna is a room or building designed as a place to experience dry or wet heat sessions or an establishment with one or more of these facilities.

https://en.wikipedia.org/wiki/Sauna

There are different kinds of saunas. Nobody gets into a 90c humid sauna, that would just kill you.

No, it seems saunas have very low relative humidity except for briefly after you splash the hot rocks. "Relative" is the key term there: the absolute humidity is high, but the hot air can accept much more H20 and it will suck moisture off your body. So it is a dry environment according to humans.

According to this company plus some sketchy math I just did, the relative humidity can swing between 15% and 40%: all over the place, but generally pretty dry. https://www.vaisala.com/en/blog/2024-12/can-you-handle-heat-...