Winterlong! I enjoyed it very much. It shared a cover with an issue of Omni in the early 1990s.

I own copies of the two sequels and would gladly loan them, but I live rather far away. WorldCat says the New Haven Free Public Library has a copy of Icarus Descending, as do a few other libraries in CT--but Aestival Tide is harder. (Is Danbury near you?)