While the OP seeks a synonym for “does not matter,” by the time I arrived on the scene @Catija had already submitted a perfectly apt response, after which, if the adjective “irrelevant” wasn’t acceptable, all that was required to find one that was, was a quick googling of the adjective and, voila tout!---unimportant, immaterial, inconsequential, insignificant, meaningless, trivial, of no matter or consequence, of little account, beside the point, neither here nor there, etc., etc., etc.---so, rather than pursuing that, I turned my attention to a different problem I saw with the OP (writing), one that I thought would have even more bearing on the quality of FreshAir’s final product.
The problem I saw was this:
1. The first sentence claims that the residents of City X enjoy favorable living conditions.
2. The second sentence significantly qualifies the first sentence, yet must be accounted for.
3. The third sentence seeks to diminish the import of the second sentence (which brings us back to the gist of the OP) by seeking a formal stand-in for “this does not matter,” i.e., the periodically heavy precipitation.
Although each sentence of this paragraph is undoubtedly true and valid, each sentence also recedes from the import of the preceding sentence.
Aside from completely reconstructing the paragraph, I believe the solution to the problem lies in a slight rewording of the second sentence and its merger with the third, while avoiding the use of “this does not matter,” or any of its synonyms.
The heavy precipitation that occurs from time to time does matter. It matters to the validity of the first sentence, it matters to the residents of City X, and it will matter to those who read the report.
Though it can probably be improved, here’s an example of the rewording and merger I spoke of:
"The residents of City X enjoy favorable living conditions. Due to the occasional heavy precipitation most residents have adopted the habit of working from home."
I apologize if my first answer was indecipherable, and I surely hope this is better.