For an equatorial island, Siptah is awfully cold. I haven’t looked at the heat map in DevKit (too lazy to re-download it, sorry) but I have yet to find even one place on the island where the temperature bar goes up. Period. It starts at neutral and only goes down from there.
Which would be okay if it weren’t for the fact that it renders at least half of the armor sets more or less unusable – perfectly wearable near sea-level, but inadequate if you go into either dead city or anywhere near the tower.
I haven’t checked any of the Elder Vaults yet. At least one of them, which seems to have fires almost everywhere, ought to be hot? But if they aren’t, then you just invalidated half of the outfits in the game, including several of the DLC armors.
(I think it would be fun, on some level, if one side of the island was a lot hotter than the other. That way, if alliances formed by side of the map, they’d naturally have recognizable uniforms. Ish.)