No, you would be cooked, but I had a hunch that obviously people already tried to see how long you could stay inside and yes there was a competition in Finland exactly for this: https://en.wikipedia.org/wiki/World_Sauna_Championships#2010...

I said "was" because 2010 was, in fact, the last edition of the event:

> On 7 August 2010, two competitors were removed from the sauna and brought to the hospital in critical condition after six minutes of 110 °C (230 °F) heat

I don't think anyone is capable to sit in a 90-100C sauna for a whole hour without breaks, otherwise with breaks I surely have been in a sauna for more than an hour.

Just this summer I was at a cottage by Vänern (the largest lake in Sweden), the sauna was built right at the lake with a pier setup for jumping into it, we had a party going late into the night where you constantly moved from the sauna into the lake, out of the lake, have chats, a beer, into the sauna again, rinse and repeat for some 8-10 hours. I have no idea exactly how long I was in the sauna but it was definitely more than a couple of hours in the whole affair :)

> I assume going to sauna takes an hour, [...] but beyond that the minutes inside/outside are a mystery...

I understand that as the general act of getting up, starting the sauna, going for your clothes change, resting a couple times, going to the kitchen for water, shower, switch off, kitchen again, whatever... you've filled an hour of your time.