Ever notice that country rain smells so much better than city rain, especially after a long dry spell?
In short, it's because the smell of rain isn't in the droplets themselves but is a blend of environmental contributions. For nature to produce that sweet, clean, fresh smell it needs...well...nature.
Plants are a key contributor, especially after periods of drought. In arid times, some plants secrete essential oils into the environment. When the rain finally comes the aromas are released into the air. These airborne scents mix with those wafting from forests where moist conditions foster the growth of geosmin, a chemical produced by soil-loving bacteria. The pounding of the rain releases their musty yet pleasing aroma. The third major ingredient is ozone, which provides the clean, almost chlorine-like, notes.
Beyond its chemistry what makes it so appealing could be explained by evolution. Anthropologist Diana Young, based on her cultural studies in West Australia, found that people associated rain with the promise of growth and replenished food supplies.