Truly the bring the first raining the smell come out everytime when the rain have with the dry soil, I do notice that as well.

But I don't know why it do smell like, but with this I think you have make you to understand something about the smell.

And what is called petrichor, is bacteria is streptomyces
bacteria,it produce geosmin molecule.

Thank for your post I learn from it and it good to always notice and know the meaning.