I wanted to know more and found this blog article by Joseph Stromberg of the Smithsonian What Makes Rain Smell So Good? | Surprising Science .
A summary for parents and teachers to talk about with their kids:
- The smell is a combination of plant oils and bacteria in the soil, which the rainwater has released into the air.
- After a thunderstorm it can also include Ozone, a molecule created by the electric charges in the air.
- The article also suggests that rain smells good to us because, whether we are aware of it or not, we associate it with new growth that brings with it a good supply of food.
I guess, if you are in a built up area of asphalt and concrete, the smells released from the ground are less likely to be from plants and soil, and more likely to be from cars and dust. Does that still smell as good to us? I'll be testing this out after the next rain.