The commenter you’re replying to is using a common English colloquialism: “go out.” In this particular construction, “go out” is short for “go outside,” which generally refers to the act of transporting one’s physical body (assumed to currently exist inside a structure, underground, or somehow contained within some sort of boundary) to a location that could be considered exterior to their present location.

In the context of the thread, the commenter is inviting those making claims about the air temperature to experience it for themselves by exiting their current containment units and exposing their sensory organs to the actual air temperature of the external world, thus providing the counterpoint to their proposition.

For the beginning of the sentence, please see:

[https://knowyourmeme.com/memes/my-brother-in-christ]

Wow. I didn’t need another reason to stay away from the NMS Galctic Hub, but the universe provides.