[firefoxman1]

It also doesn't answer my main question: Why does the air smell good right before it rains. I'm sure being able to smell rain coming had evolutionary advantages...but how does it work?

[cxseven]

It's probably the smell of ozone and ions causing particles in the air to adhere to surfaces, cleaning it like how electrostatic air filters work.

http://www.madsci.org/posts/archives/1998-08/897083302.Ch.r....

[Kliment]

Moist air coming down. Has the same effect, just less so.