TOLEDO, Ohio — Rain showers are one of Mother Nature's most common occurrences. We often ask ourselves on any given day if it's going to rain, if we'll need an umbrella and if we should reschedule any outdoor plans.
But have you ever asked yourself why you can smell the rain before it gets to where you are? There are three possibilities for this.
Raindrops help release the earthy-smelling chemical "geosmin" into the air
The Merck Index, an encyclopedia of chemicals, drugs and biologicals, defines geosmin as the “major volatile component of beet essence, also ... the potent earthy odor contaminant of fish, beans, [and] water. The human nose can detect it at concentrations in air as low as 5 [parts per thousand]."
When rain showers arrive in your area, pollen acts as the same as these earthy-smelling chemicals, where it is lofted in the air as pollen particles and chemicals, worsening allergies and causing the smell of rain.
Ultimately, raindrops force spores into the air. The good news is this process in which we inhale the smell of rain is nontoxic, nor is it harmful to us.
Plants secret oils during extended dry periods of weather
Another contributing factor to the smell of rain is the release of plant oils. During dry periods, stearic acid, oleic acid and palmitic acids latch onto plants and act as a grease. When there is rain on the way, the odor that is released from these plants gives off a particular smell called petrichor. This term is the most common reason why we smell rain.
According to EarthSky, a website that publishes Earth and space news, "Petrichor is a combination of fragrant chemical compounds. Some are from oils made by plants. The main contributor to petrichor is actinobacteria. These tiny microorganisms can be found in rural and urban areas as well as in marine environments."
After this process happens and rain showers go away, the smell is weakened by the evaporation and drying of these plants. Typically, the strongest rain smells can be found in wooded areas and fields. The more greenery that is around, the more oils and aids are released into the air.
Thunderstorms and lightning can split oxygen molecules into individual atoms
Oxygen molecules are all around us every day; it's how all beings on earth breathe every second of the day. If you add lightning, and thunderstorms to this component, we have the splitting of atoms.
This process is one of the rare and uncommon reasons why we smell rain showers and is only detectable in the immediate aftermath of a lightning strike.
When oxygen molecules are split into individual atoms, they latch on and combine with O2 molecules, making what we call ozone.
Although this process is one of the rare breakdowns, anytime this happens there is a distinct smell in the atmosphere.
