365
Who's taking showers so hot that steam comes off? A quick web search says showers should be colder than 40°, maybe up to 42.5°. Phones start thermal throttling when battery temp reaches 45°. So shower water is hotter than the recommended operating temperature of 0 °C to 35 °C, but not hotter than what the phone itself can get.
The manual says sudden changes in temperature such as the sauna may damage the water resistance.
May doesn't mean will. Mind you that the manual also says installing unofficial apps voids your warranty. I wouldn't be worried unless someone actually tests this and finds that it does cause harm.
Edit: Did I say something wrong? I don't understand the downvotes