Why does the ground smell after rain?
Short answer
Rain itself is not usually the source of the strong smell. Instead, rain helps move plant-derived substances and chemicals made by soil microbes from dry ground into the air.
How it works
Dry soil and rock surfaces can hold oils from plants. Soil microbes can also produce a substance called geosmin, which has an earthy smell. The earthy scent after rain is sometimes called petrichor.
When raindrops hit the ground, small air bubbles can form and burst. The bursting bubbles can carry tiny droplets containing scent molecules into the air, where they can reach our noses.
Key point
The smell can be easier to notice after a long dry spell or during light rain. Its strength and exact ingredients depend on the soil, plants, microbes, and the way the rain falls.