The thermosphere has extremely low density gas particles, so heat transference is minimal. A reflective surface and smart heat radiance takes care of those extreme temperatures.
yes, you can put your hand in a pot of water at 90 degrees C and sustain serious injury immediately, however you can sit in a sauna with an air temperature of 90*C happily for quite a while.
you could indefinitely were you to find a way to radiate heat off yourself as the ISS does. A sauna, unfortunately, is a closed system while the ISS can radiate heat into space.
