1980s series of books about Ice and Fire?

Question

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.

Answer 1

This sounds like the Lear's Daughters series by Marjorie B. Kellogg and William B. Rossow. There were two novels: The Wave and the Flame and Reign of Fire.

I remember the names of some of the members of the science expedition: Megan Levy, Stavros Ibia, Emil Clausen, Veronica McPherson.

The natives of the planet were a race of small humanoids called the Sawls, and the names of the ice and fire goddesses that they worshipped were Valla Ired and Lagri. The were believed to be primitive at first, but in a later scene they show one of the scientists a diagram that turns out to be periodic table of the elements including elements beyond those discovered so far by humans.

A plot summary of The Wave and the Flame from fantasticfiction.co.uk:

The planet Fiix has a climate of bizarre extremes which defies conventional scientific explanation. An expedition from Earth, expecting to find a desert planet, instead finds itself marooned in the middle of a savage winter. The local population, the Sawls, are small and apparently primitive creatures; but while Emil Clausen - mineral company representative in search of profits from the planet's lithium deposits - and planetologist Tay Danforth are missing, presumed dead, after being caught in ferocious floods, other scientists start to learn that the Sawl's have a complex and surprisingly advanced culture. In particular, linguist Stavros Ibia begins to identify with the Sawl's and determines to protect their planet from commercial exploitation, and to gain an understanding of their theological and historical roots.

Answer 2

I thought at first that it was novel The Snow Queen, by Joan D. Vinge, and its continuation The Summer Queen. As you're asking abut something different, then I think it is the Heliconia Trilogy, by Brian Aldiss:

It is an epic chronicling the rise and fall of a civilization over more than a thousand years as the planet progresses through its incredibly long seasons, which last for centuries.

The trilogy consists of the books Helliconia Spring (published in 1982), Helliconia Summer (1983) and Helliconia Winter (1985).

Helliconia lies in a loose binary star system, which consists of a yellow-orange dwarf similar to our sun, Batalix (spectral class G41), and a hotter and brighter white star, Freyr (Type A supergiant). Helliconia orbits Batalix, which in turn orbits Freyr.