I’m in the US and it was 40C (104F) yesterday, which is normal for my area. I spent the whole day either indoors or in the neighborhood pool, and it was perfectly comfortable.
Look at posts and comments from the instance admin. Does this person seem to know anything about running a server or managing software? Do you like the admin’s tone and attitude? Does it seem like the instance will be around for the long-term, or is it someone’s hobby that they may abandon on a whim?
Look at the instance’s ban list. Do you agree with the choices? Maybe you want your All feed to include exploding-heads and lemmygrad, or maybe you don’t.
Does the instance seem to have a community theme that you want to be associated with? Some emphasize LGBTQ+ communities, or NSFW content, or particular political views.
Usually you have to be a resident for a number of years before being eligible for citizenship. Often the process is faster and easier if you meet minimum income or wealth thresholds, because countries like hosting rich expats.