I think I can sometimes smell the approach of rain. What is that smell called?
Studies have shown there is, indeed, a smell associated with the approach of rain, and it has a name: petrichor. There are several possible explanations for petrichor. The dominant vegetation of a region appears of contribute. The reaction between moisture or very high humidity and certain volatile substances in or on plants is a partial explanation. Pine forests, for example, release more terpenes into the air, substances found in medicines and perfumes. Moisture, warmth and low air pressure, conditions maximized as thunderstorms approach, enhance our sensitivity to smell while hastening the release of fragrant molecules from plants. Also, raindrops can kick up particles such as dust that lend a scent to the air.