Rain, Fog, Lightning, Day-for-Night.
You're covering a lot of bases. Each effect requires careful observation, study, practice & patience. You will fail (often), but these defeats are a good thing; it's what we call experience.
So, how 'easy' is it? Please self-assess your experience level and place yourself on the provided scale (below)
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Experienced Pro = easy.........................................................Newb = hard
YouTube has some excellent demos on how these effects might be done.