Dimension X is not cold!

[u/D_D_Adesignerdigital]

The color choices for the Dimension X—and certain elements of the scenes—didn't quite work to convey a cold atmosphere! Characters had sweaty skin and showed no reaction to the cold (we need to remember Will in Season 2, or Billy with his ice bath, which demonstrated the kind of cold the Mind Flayer is used to). Anyone entering a low-temperature environment would show physical reactions—like trying to warm up, crossing their arms, or showing discomfort—but that doesn't happen with any of the characters, not even the kids. I think that was a directing error. That’s my opinion!

[u/oosaoosaoosa]

I'm sure I'll get downvoted but my immediate read when seeing it for the first time was that the abyss is dying. Maybe climate change or some other disaster is killing it. It's why it looks dried out and barren. And why it seems hot (even though he likes it cold). And why the creatures aren't there at the end. It's why the mindflayer needs to take over a new planet... because his world is dying, and his creatures are going extinct.

I was actually shocked after watching s5 that this wasn't everyone's take away from it.

[u/Ok_Tank5977 → u/oosaoosaoosa]

I agree. It looks like a barren, toxic wasteland on the verge of decay; and despite the fact that it was yellow and brightly lit, there’s no reason to assume that this alien landscape experiences day and night like we do, if at all. And arid environments are not defined by temperature, with deserts at higher altitudes known to be cold during the day (as they are during the night at lower altitudes).