Read this between '90-'93, so was published before '93 at least. The main character was a guy. It was about the sun doing something, moving away or whatever and the world was turning really cold. He decides to get out of the city and meets a girl along the way. I don't remember much of anything else, but the end was that they were together, in a shelter (possibly a kid or alone.) That is all I remember. I swear it either had the word 'sun' or 'black' or something like that it in. I think it was a mass market paperback and probably published sometime in the '80's or early '90's. Not much info, but hopefully someone knows the book I'm talking about. Thanks!

that  it  may   have been a paperback  that I read also.  try 'Grey Beard"

I know the story "A Pail of Air," but it's very short and is about a family, so no romance.  Also, it's got to be close to 60 years old.