There are two things I feel that people get wrong with Saunas:
You do not have to count down 15 minutes in the sauna whilst watching a sand clock.
You go in and leave the sauna when you feel like doing so. I have a personal routine of going about 5, 10, 5 minutes with a couple of minutes break between with warm showers. You generally have to wait at least ten minutes after the last turn to prevent “sauna sweats” when you have all your clothes back on and resume your normal activities.
On regards to temperature. It does not have to be like 100 degrees! Most saunas I goto are around 80 degrees celcius after steaming up the place a fair bit with warm water on the hot stones.