Did you ever notice that you can smell rain? Usually, you smell it better after the rain, but if you are a highly trained naturalist, or Aragorn son of Arathorn, Elessar, the Elfstone, Dúnadain, the heir of Isildur Elendil’s son of Gondor, or something, you can smell it before it rains. During the rain you are usually inside smelling other things.

It is called Petrichor. That word comes from ancient Greek for rock (obviously) and God Blood. That makes sense because with all the gods up in the sky, a certain amount of God Blood would fall to the earth when it rains.

Anyway, I came across this video on Petrichor, possibly explaining it.

So, basically, you are smelling raindrop spit.