This is before it actually starts raining, so it’s not wet asphalt or anything. Why does cooler, more moist air smell differently?
You answered your own question. Moist air carries smells better than dry air.
Usually before a shower, the winds will pick up due to the convection around the shower. The winds will be coming off the rainshower and blowing in your face before the rains begin. Sometimes the shower will bypass you and you’re left with nothing but the aroma…and perhaps the smile. You may get hit by a tear or two, blown in by the wind even if the storm bypasses you.
I don’t know much about this site, but it offers this:
Our humidity stays above 75% a good deal of the time, so I’m not sure how precise that is.
If there’s lightning before the storm, you may smell ozone.
And maybe the winds and moist air are wafting some actinomycetes around which we associate with rain?
Close, but no banana.
You smell rain because it’s usually rained somewhere before it gets to you, and the winds carry the smell of wet dust, etc to you.
Rainwater has little or no smell of it’s own.
Peace,
mangeorge (Who loves the smell of rain)
I was just going to say the same thing. The wind that picks up before it rains is coming from somewhere where it has already rained. So various things like cement and plants are wet, and wind blows by them and picks up their odors and carries it to the places where it’s about to rain.
I had always heard that it has something to do with the lower air pressure that occurs prior to a storm allowing the normally lower to earth smell of rotted vegetation and other earthmass to rise higher in the air (I’m serious). I have no idea whether this is true.