Keystone Science School explains why it smells that way after a rain |

Keystone Science School explains why it smells that way after a rain

Dan Van Horn leads a hike with an educational mission as part of his work with the Keystone Science School.
Keystone Science School | Special to the Daily

Over the last four years as an outdoor education instructor I have worked with thousands of students and adults in beautiful places across the country. Needless to say I have had the opportunity to share my knowledge and connect with a great deal of people. They weren’t the only ones that were learning, however; I was soaking up endless amounts of knowledge about nature as well. The truth is, with my background in biology, most people don’t want me to give them a quick lesson on organic chemistry or teach them about microbiology. Although when I point out a constellation or share a fun fact about an aspen tree, they’re thrilled with their new piece of information. So with the uncharacteristic amount of rain we have had all across the state this fall, I thought I’d share an interesting fact about liquid precipitation.

Do you love the smell of rain? I can’t tell you how many times I have heard students and adults say how much they love the smell of rain. I have to agree; that earthy aroma that fills my nose after it just starts to rain is one of the best smells nature can provide. A few years ago I had an inquisitive student ask me why rain smelled that way. I didn’t know the answer, but I of course had to find out. So here’s the story, before a rain shower and directly after one, there is a higher moisture concentration in the air. This extra moisture allows for scents that are already present in the environment to be magnified. Oils from trees and plants are carried more easily in the now-humid air. To put this into perspective think of an aerosol can, one that is supposed to smell like laundry linens. When you spray it, the scent is carried in the moist air.

But, that’s not the only thing causing that natural odor; bacteria called actinomycetes play a big role as well. We all know that bacteria lives just about everywhere, from the newspaper you are holding, to super-hot vents deep in the sea, to your own stomach. It probably isn’t a big surprise that there are thousands, if not millions, of species of bacteria that live in soil. Just one of those little guys, the actinomycetes, create spores that lay dormant in dry soil. As rain begins to fall after a significant dry spell those spores are kicked up into the air and inevitably find their way into our noses.

Spending time outside with students has allowed me to learn more about the environment than I thought I ever could. As an educator I am always trying to learn new interesting facts that I can share with the kids. But sometimes, the experiences we have playing in the rain, strolling through aspen groves or climbing mountains gives us more knowledge than we realize. Maybe the most important thing is for us to just get out there and experience out natural world firsthand.

Dan Van Horn is a Program Instructor at Keystone Science School. For more information on Keystone Science School, give us a call at (970) 468-2098 or visit

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