You're BOTH right...
The narrator of the story beleives that the Sun has unexpectedly gone nova and that he has only one night to live, but at the end of the story the flare subsides just before dawn and he realises humanity will survive.
(Modern studies of atmospheric dynamics make me boggle at the idea that one side of a planet can be scorched bare and on the other they can keep eating their cornflakes at breakfast time without worrying about more than a light wind)