Unveiling the Science: What Makes Rain Smell So Good?

LOUISVILLE, Ky. (WAVE) – That comforting “smell of rain” is real, and it’s not just in your head. Our noses can pick up on special scents that come from the ground when it rains.

This earthy aroma, called petrichor, is created by a mix of different fragrances released when raindrops hit the soil. Australian scientists first named it petrichor in 1964.

You often notice this pleasant scent when humidity levels rise just before it rains. But once the rain begins, that smell becomes even stronger.

Here’s how it works: when raindrops land on dry ground, they release tiny molecules trapped in air bubbles in the soil. The wind then carries these airborne particles, allowing us to smell petrichor.

There are three main scents that make up petrichor: ozone, geosmin, and plant oils.

When lightning strikes, it breaks apart oxygen atoms, creating ozone. After rain, this ozone drifts down from the sky, mixing with the air we breathe. If you want to learn more about ozone’s smell, you can check out this link.

Another scent, geosmin, comes from actinomycetes, tiny bacteria that live in the soil and water. When raindrops hit the ground, they scatter these bacteria’s spores into the air. Don’t worry, these spores are harmless! In fact, they help break down organic materials. Interestingly, humans can detect geosmin at very low levels—around 10 nanograms per liter, which is like a penny in a billion dollars. More about this can be found here.

Additionally, plant oils like oleic acid and stearic acid become more noticeable after a long dry period. These oils build up on leaves and ground surfaces during dry weather, and rain releases them into the atmosphere. It’s believed that these oils help seeds survive by slowing down germination, allowing them to conserve water.

Interestingly, light to moderate rain is best for releasing these scents. If it rains too hard, the intensity can actually prevent those tiny particles from entering the air properly. You can read more about this phenomenon here.