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]
A People's History of The United States, Howard Zinn
The Myth of Sisyphus, Albert Camus
A Short History of Decay, E. M. Cioran
The Book: On the Taboo Against Knowing Who You Are, Alan Watts
Discipline and Punish, Michel Foucault
The Selfish Gene, Richard Dawkins
How Emotions Are Made, Lisa Feldman Barrett