The Complex Chemistry Behind the Rain’s Scent

This distinct aroma is due to three main chemical processes: petrichor, ozone generation, and geosmin production.¹ Petrichor is the term used to describe the smell produced after rain falls on dry soil or rocks. The post-rain smell comes from airborne organic molecules mixing with mineral surfaces. When it doesn’t rain for some time, these molecules mix with other elements on a rock’s surface, releasing a combination of things that make up petrichor.²

The second chemical process involved in this unique pre-rain scent is the inclusion of ozone. During a thunderstorm, the electrical charges can heat oxygen and nitrogen molecules in the atmosphere, which then can recombine into O³, ozone. Ozone has a sharp, pungent scent and is often described as akin to fresh linen.³ This smell is typically associated with the electricity-charged atmosphere of stormy weather rather than light rain.

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