why does rain have a smell to it?

Answer 1

Believe it or not, the smell comes from bacterial spores that live in the soil. The rain kicks the spores up into the air where we breathe them in. They have a very distinctive earthy smell, which I absolutely love!

Sidenote: in the town I grew up in, we had an onion procesing plant to the south. Whenever rain was on the way, we would tend to have a southerly wind. The higher humidity brought out the oniony smell, and the south wind would blow the smell into town. So if it smelled like onions outside, we knew rain was on the way!

Answer 2

While bacterial spores provide some of the scent, the main part of the scent is petrichor. Many plants contain volatile oils which evaporate. It is these that provide the scent of flowers and leaves. The evaporated oils are absorbed by the rocks and earth where they collect. Falling rain splashes them back into the air and we smell them. Thirty or so years ago an Italian company extracted it from rocks and sold it as "Earthscent.

Answer 3

if you mean before it actually rains, but is threatening, it's because the downdraft brings with it ozone which has that "wet earth" smell to it

Answer 4

maybe because it is slightly acidic?