Thunderstorms now heading through eastern part of the state

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Have you ever stepped outside after a summer rain and immediately thought, “Wow, it smells amazing out here!” That earthy, fresh, almost nostalgic scent has a name: petrichor.

As someone who has always been fascinated by storms and rain, I often found myself saying, “I can smell the rain,” or “I can smell a storm coming.” It turns out I wasn't imagining things. There is actually a perfectly good scientific explanation for why some of us can detect an approaching rain shower before the first drop falls.

It's one of nature's most beloved fragrances, and despite what many people think, you're not actually smelling the rain itself. You're smelling a fascinating mix of chemistry, biology and weather working together.

During dry periods, plants release oils that accumulate on soil and rocks. At the same time, soil-dwelling bacteria produce an organic compound called geosmin, which is responsible for that classic earthy smell. 

Geosmin is incredibly potent. Humans can detect it at remarkably low concentrations. We can smell geosmin at concentrations as low as 5 parts per trillion, a sensitivity that surpasses a shark's ability to smell blood in water.

When rain arrives, the impact of raindrops traps tiny air bubbles that burst upward like microscopic champagne bubbles. These bubbles launch aerosols into the air, carrying geosmin and plant oils straight to your nose.

It’s best noticed after a longer dry spell, followed by a light to moderate rainfall. 

And petrichor isn't always the first scent to arrive before a storm. Sometimes your nose picks up a sharp, clean smell even before the rain begins. That's ozone, a gas made of three oxygen atoms, created when lightning splits the atmospheric oxygen and nitrogen molecules.

Strong storm downdrafts can carry that ozone-rich air toward the ground, allowing some people to smell an approaching thunderstorm before the first raindrop falls. Once the rain arrives, however, petrichor takes center stage with its earthy blend of plant oils and geosmin.

So the next time a rain shower rolls through and that unmistakable aroma fills the air, take a moment to enjoy it. You're experiencing a blend of weather, biology and chemistry.

Weather and Climate News

Updraft® - Minnesota Weather News

Mandy Thalhuber

Author

Have you ever stepped outside after a summer rain and immediately thought, “Wow, it smells amazing out here!” That earthy, fresh, almost nostalgic scent has a name: petrichor.


A whiff of weather, can you smell the rain? Science says yes

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