In the 80s, I read a pair (possible trilogy) of books about Ice and Fire and a planet with a very slow orbit. The orbit may have been highly elliptical around twin suns — but I'm not sure about that last point. The orbit was so slow it took centuries for the climate to change. The first book dealt with the end of winter and the onset of spring while the second was about the planet going into summer. I remember there being a (possibly marooned) science expedition and them trying to figure out the planets strange weather patterns and the planets natives belief in 2 goddesses battling for control of the planet.
What were the name(s) of these books or the author of them?
This was long before George R.R. Martin's A Song of Ice and Fire series with Game of Thrones.