Why is it that a couple minutes prior to a rain storm, a distinct smell appears in the air.?

Question

It's kind of a musty smell, and usually appears 2-3 minutes before a storm, sort of dissipates during the storm and then is usually gone after the shower. In a way it's sort of like having the ability to smell the rain coming.

Answer 1

Mmmm, I miss that smell.  In Texas, it was so strong and almost alluring...it was just different.

I read somewhere that it was the build up of moisture in the air and something to do with air molecules either expanding or compressing or something like that.  It might've been stronger in Texas because of the super crazy lightening storms.  Here in California, I really don't smell it as much.  Just an extremely strong woft of designer imposter perfumes...oh, buurrrrrn!   Sorry...I had a moment there.

Answer 2

You must have smelt the same smell when u pour water on dry, hot sand. Couple of minutes before it rains, it must be raining in some other area near to u, and rainstorms occur mostly during summer so that is why this smell occurs as the sand is hot. I live in Chennai,india. Here it rains very heavily during winters and it rains during summers. I smell this smell only in the summers but not in the winters. Moreover this smell occurs for only few minutes as the sand becomes cooler if there is more water. In tamil(my mother tongue) this smell is called " mann manam."  Mann = sand, manam = smell.

Answer 3

I don't know.

i've always wondered the same thing.

Answer 4

you are right but it is actually the smell of the chemicals in the "acid rain"

Answer 5

your right, your actually smelling the moisture, the reason you dont smell it afterwards is because your probably used to it

Answer 6

I have always suspected that, as the storm approaches, the barometric pressure drops and air that is trapped in the porosity of the ground diffuses out and you get that sort of earthy smell.

I used to work at a place that was right next to the town land fill (dump), I could always tell when it was going to rain because it would smell much worse than usual, persumably because the drop in air pressure would let some of the putrid vapors from the burried garbage (garbogen?) diffuse out of the ground.

Answer 7

Rain striking the ground knocks certain bacteria into the air, namely Actinomycetes, and that is often the cause of that musty smell.  You smell them before the rain starts because it is already raining nearby, and the smell is carried to you before the rain.