Are you one of the few people who can smell the presence of rain is in the air? The world is firmly divided into two camps: those whose noses smell when it rains and those who believe such occasions are utter nonsense. While not everyone can smell the rain before it starts, there is actually scientific evidence that some people have this ability.
People with a good sense of smell can often detect an odour that Scientific American says has a "sweet, pungent sound" likened to chlorine bleach. This is due to ozone, which can be released from things like fertilisers and paints, as well as from natural sources. Ozone can be created by an electrical charge that signals an imminent storm. Downdrafts from thunderstorms can carry high-altitude ozone to ground level and into our nostrils. While people's ability to smell ozone varies, there are people who can pick up even the tiniest hint and know it's probably time to grab an umbrella.
Another term associated with the smell of rain is petrichor. This word refers to a potpourri of scents that appear after the rain. All that falling water lifts many molecules that create flavours. First coined in 1964 by mineralogists Isabelle Joy Bear and Richard Thomas, petrichor is formed when airborne molecules from decaying plants or animals settle on the surface of rocks. When it rains and falls on the surface, the water droplets burst and release these fragrances into the air. Most people are also familiar with the smell of damp earth that occurs after a downpour. This distinctive odour is due to a chemical compound called geosmin. Despite the earthy smell, geosmin does not come from dirt. It's actually a byproduct of Streptomyces bacteria.
Research has shown that these bacteria have spores that contain geosmin and that it is used to attract insects and other animals, allowing those spores to spread over more soil. Why is the smell of rain so widespread? A 2015 study showed that drops of water that fall to the ground trap air inside. When the air bursts the droplet, it creates aerosols that spray any scent onto the floor. These aerosols can spread quite far, so that depending on the amount of precipitation, a rather strong odour of geosmin can be perceived. So next time someone tells you it smells like rain, now you know they probably smelled ozone. And when someone mentions what it smells like after a shower, you can impress them with your knowledge of what it actually smells like.