The smell of rain comes from soil bacteria that release a chemical called geosmin.

The scent of rain is called petrichor. Australian researchers Isabel Bear and Richard Thomas first named it in 1964. They found that plants release oils during dry weather that soak into the soil. When rain falls, these oils mix with a chemical called geosmin.Geosmin is made by Streptomyces bacteria living in the dirt. In 2015, scientists at the Massachusetts Institute of Technology used high-speed cameras to watch raindrops hit the ground. They saw the water trap air bubbles that burst like tiny cans of soda. This spray is called an aerosol.The wind carries these aerosols for long distances. This is why you can often smell a storm before it arrives. Humans are very good at smelling geosmin. We can detect it at five parts per trillion.This means we can smell it better than a shark can smell blood in the ocean. This skill likely helped early humans find water in dry areas. The bacteria that make this smell are also useful in medicine. They are used to create many of the antibiotics doctors use to treat infections today.