Petrichor, the smell produced by a combination of oils and chemicals, heralds the end of a dry spell
There is something satisfying about the smell of rain. It is an aroma that is particularly noticeable at the end of a dry spell in summer. Some would claim it is a figment of the imagination but it is a real smell called petrichor, although the name is rather pretentious, made up by two Australian scientists who discovered its origins in 1964. The word comes from the Greek words for stone, petra, and ichor” the golden fluid said to be in the veins of the immortals.
The source of the smell is a combination of oils and chemicals. In a dry spell plants secrete the oils to signal the halt of root growth and seed germination, while the chemicals come from the reactions of bacteria.