It rained. In May. Just goes to show how intense climate change has gotten. These unexpected showers in Mumbai are thanks to unusually strong western disturbances.
But that’s not what we’re here to talk about.
Yesterday, after the rain and wild winds had passed, my family and I decided to head out for a long drive. The weather was unusually pleasant, so I asked if we could roll the windows down. The moment we did, a strong, earthy scent of herbs and plants rushed in. It was like my olfactory nerves had just been treated to a five-star experience.
“I don’t remember it smelling this strong after the later rains,” I wondered aloud.
And that got me thinking—what’s the science behind this?
This phenomenon is known as petrichor.
So what causes it? Let’s break it down:
1) Plants and soil prepare ahead of time:
(Maybe take notes from them… just saying.)
During dry spells, plants secrete oils into the soil. These oils hang around, waiting for the rain to break them apart—not a study strategy you should adopt, though. Go study, please.
At the same time, a group of soil-dwelling bacteria called actinomycetes (very hardworking, by the way) produces geosmin—the compound responsible for that earthy smell we all associate with rain. It’s probably also the reason behind those fancy petrichor-inspired dishes (yes, I keep thinking about food).
2) Cue the rainfall (Just…maybe not in May?)
When the first rain hits the ground, it breaks apart those oils and geosmin molecules, sending them airborne. And just like that, the earthy scent hits your nose.
THE OZONE LAYER
Sometimes, especially during thunderstorms, the rain smell has a slightly metallic or sharp tang. That’s because ozone is carried down from the atmosphere by wind before or during the rain. Yup, the same gas that protects us from the sun. (And no, this is not an excuse to skip sunscreen.
Why only the FIRST rain?
You mostly notice petrichor during the first rain because that’s when the soil is full of those dry-weather oils and geosmin. Later rains don’t have the same dramatic effect—it’s like third-wheeling your own friend group.
Well, third-wheeling or not, all rains are equally important. And now, you’ve got the science behind that amazing, earthy smell that fills the air after a downpour. So the next time you roll down your window after the rain, take a moment to appreciate not just the fresh air, but the little wonders of nature at work.
