I think it is clear that these concepts are relative and are interchangeable, comparing to Semitic beliefs, we see a land of fire is considered both as a hell and a heaven, it certainly depends on where you live, for Ancient Iranians who lived in a very cold climate, the worst thing could be more coldness, for this reason they attributed coldness to Angra Mainyu (Ahriman).
But it is interesting for me that after migration to the Iranian plateau, they again mostly settled in the cold mountainous regions, maybe they had a different concept of their warm heavenly land or didn't want to forget the climate of their original land!