Many people have experienced it: a strange but familiar scent in the air just before a storm arrives. For generations, people have described it by saying they can “smell the rain coming.” But is this just imagination, or is there actually science behind it?

Interestingly, scientists say there is a real explanation for this phenomenon. The smell most people notice before rainfall is known as petrichor. This scent is produced when rain interacts with certain compounds in soil and plants. During dry periods, plants release oils into the ground, and bacteria in the soil produce a compound called geosmin.

When the first drops of rain hit the ground, tiny air bubbles form and release these compounds into the air as aerosols. These particles carry the earthy scent that many people recognize as the smell of rain.

In addition to petrichor, approaching storms can also produce ozone, a slightly sharp scent that sometimes appears before heavy rainfall or lightning. Sensitive noses may detect this smell even before the rain begins.

So when someone says they can smell rain coming, they might not be imagining it after all.

The next time you notice that fresh earthy smell in the air, it could be nature’s subtle signal that rain is on the way.