The typical "spaghetti western atmosphere" is of course the one where there is a shanty ghost town, a desolate landscape, and the wind is blowing all the time.
People are unshaven and wearing dirty clothes, and don't talk much.
The "Sergio Leone/Fistful of Dollars atmosphere" that started the spaghetti western genre in the 60s.
This is the basic atmosphere, that apparently was quite different to the clean and civilised atmosphere, or maybe lack of atmosphere, of the American western movies of those days.
As times went by, different atmospheres, or perhaps more correctly different "styles" emerged within the SW genre.
Some were pretty humorous, others very downbeat, or even gothic.
The musical soundtracks were of course also a major contributing factor to the atmosphere of these films.