Slight hyperbole, but nuclear reactors in Switzerland and France shut down more and more often because the water needed to cool them down is already too hot:

https://www.swissinfo.ch/eng/climate-adaptation/beznau-nucle...

It is far from boiling, but these limits are there to avoid killing all life in the rivers.

I think it would be more accurate to say "avoid killing the most vulnerable life" crossing the line would not be the end of the world.