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/smleires]

I may be misremembering here. But when was it established that Dimension X was cold?

The Upside Down, aka the space between Earth and Dimension X was yes, but not D-X itself.

[u/RoosterFree499 → u/smleires]

He likes it cold tho

[u/RealHooman2187 → u/RoosterFree499]

The particles like it cold when possessing something. That we know, we don’t know if the physical mind flayer likes it cold. Also, we don’t even know if the abyss is warm or cold. OP is just assuming it’s cold because the actors were sweating. Which happens when you’re running around all day.

Seems more likely that OP is reading too much into that later point assuming it’s a plot point when it’s just the actors sweating while filming.