Why Some People Can Smell Rain Before It Falls
Weather science hidden in plain scent
A familiar earthy fragrance can sometimes reach your nose before the first raindrop lands where you are—but the explanation involves soil microbes, plant compounds, moving air, and the chemistry of a storm.
Rainwater itself has very little odor. What people call the “smell of rain” is usually a changing mixture of airborne molecules released from the ground, vegetation, pavement, and atmosphere. The timing matters: the scent noticed before a shower is not always the same scent that rises after drops strike dry soil.
Outflow from a nearby shower can carry earthy aerosols toward you even while your own location is still dry. Thunderstorm downdrafts may also bring sharp-smelling ozone downward.
When drops hit porous ground, tiny trapped bubbles can burst and launch microscopic droplets containing odor-producing compounds into the air.
This powerful-smelling natural compound is produced by microorganisms, including many Streptomyces bacteria, and is readily noticed by the human nose.
Can people genuinely smell rain coming?
Yes—but not because approaching raindrops send out a single universal “rain molecule.” A person may be detecting several environmental signals at once. Rain may already be falling upwind, where droplets have released earthy-smelling aerosols from dry soil. Gusts at the leading edge of the weather system can then transport those aerosols beyond the rainfall itself. In a thunderstorm, descending air may also carry ozone from higher in the atmosphere toward ground level, producing a sharper scent that some people describe as clean, metallic, electrical, or chlorine-like.[3][4]
Higher humidity may contribute as well. Moisture can help release compounds stored on porous mineral and soil surfaces, although the strongest burst of the classic earthy aroma generally occurs once rain physically strikes the ground.[1][3]
Petrichor describes the characteristic earthy aroma associated with rain on dry ground. It is often strongest during or just after the first light rain—not necessarily before rain begins at the observer’s exact location.
What exactly is petrichor?
The term petrichor was introduced by Australian researchers Isabel Joy Bear and Richard G. Thomas in a 1964 paper in Nature. Its name combines the Greek petra, meaning stone, with ichor, the mythical fluid said to flow in the veins of the gods.[1]
Petrichor is not one pure chemical. It is a scent profile produced by a mixture of substances associated with dry soil, rocks, plants, and microorganisms. During dry weather, volatile plant-derived compounds and other organic materials can accumulate on mineral surfaces. Moisture and rainfall help release them into the air, where the nose interprets the blend as the recognizable smell of fresh rain.
Geosmin: the molecule behind the “earthy” character
One of the best-known contributors is geosmin, a naturally occurring compound whose name literally refers to an “earth smell.” It is produced by several microorganisms, notably soil-dwelling Streptomyces bacteria. Geosmin also contributes to the earthy flavor of beetroot and to musty taste-and-odor problems in drinking water and freshwater fish.[5]
Humans can notice geosmin at extremely low concentrations, though published detection thresholds vary depending on the test method, the surrounding mixture, and whether the compound is measured in air or water. That sensitivity helps explain why a small amount released over a large area can create such a memorable smell.
How a raindrop sends scent into the air
High-speed experiments have shown that a raindrop striking a wettable, porous surface can trap tiny pockets of air beneath it. Those bubbles rise through the drop and burst at the surface, producing microscopic aerosols. The aerosols can carry material from the soil—including odor-producing molecules—into the surrounding air.[2]
Plant-derived oils, microbial products, and other organic molecules collect on or within soil and mineral surfaces.
The impact traps tiny air bubbles between the water and the surface.
Microscopic droplets are ejected into the air, carrying scent molecules away from the surface.
Local breezes or storm outflow spread the aerosols, sometimes carrying them ahead of the visible rain curtain.
Light or moderate rain can be especially effective at producing these aerosols under suitable surface conditions. A violent impact is not always best: very heavy drops may splash and disrupt the bubble-forming process differently, while already saturated ground may not release the same concentrated “first rain” scent.
Why some people notice it more than others
Smell perception varies widely. Human odorant-receptor genes are unusually diverse, and small genetic differences can change how intense, pleasant, or even detectable a particular odor seems. Research on human olfactory receptors has shown that receptor variation helps explain why the same molecule can produce noticeably different experiences from person to person.[6]
Biological differences
- Variation in odorant-receptor genes
- Temporary congestion, allergies, or illness
- Age-related changes in smell sensitivity
- Individual differences in nasal airflow and sensory processing
Experience and attention
- Regular time spent outdoors
- Familiarity with local soil and vegetation
- Learned associations between scents and storms
- Greater attention to wind, humidity, clouds, and temperature shifts
Experience does not necessarily make the nose physically more powerful, but it can make the brain better at recognizing a meaningful pattern. A farmer, gardener, hiker, or anyone raised in a region with distinct wet and dry seasons may quickly connect a faint earthy scent with a specific change in wind and sky.
Soil, plants, cities, and seasons change the smell
There is no single worldwide version of petrichor. The aroma depends on the local environment: the type and porosity of the soil, how long the ground has been dry, the microorganisms present, the surrounding vegetation, the temperature, and the strength and direction of the wind.
Plant oils, leaf litter, bark, fungi, and moist organic matter can produce woody, green, resinous, or mushroom-like notes alongside geosmin.
Rain can lift accumulated dust, plant material, vehicle residues, and other surface compounds, so the first shower in a city may smell unlike rain over farmland.
Long dry periods permit more material to collect on surfaces, making the first rainfall feel especially aromatic.
Once surfaces have been washed and the soil remains wet, fewer concentrated compounds may be available for the same sudden release.
What about ozone?
Ozone is a molecule made of three oxygen atoms. Near the ground it is an air pollutant and lung irritant, even though many people describe its odor as sharp or “clean.” Ahead of some thunderstorms, downdrafts can transport ozone-rich air downward, making the scent noticeable before rainfall reaches the observer.[4]
This is chemically different from petrichor. The easiest way to distinguish the two is by character: ozone tends to smell sharp, electrical, or chlorine-like, while petrichor and geosmin smell earthy, mineral, or soil-like. In real weather, the odors may overlap.
Can dogs smell rain before humans do?
Dogs possess highly developed olfactory systems and can detect environmental odors that humans overlook.[7] It is therefore plausible that a dog may notice storm-related scent changes earlier than its owner. However, a dog’s behavior before a storm cannot automatically be credited to smell alone.
Dogs may also react to distant thunder, wind, changes in routine, static electricity, or shifts in atmospheric conditions. Some become restless or seek shelter, while others show no obvious reaction. It is more accurate to say that dogs can detect a broad collection of storm cues—not that every dog has a special biological sensor devoted specifically to rain.
Frequently asked questions
Does rain itself have a smell?
Pure water has little to no odor. The familiar fragrance comes mainly from compounds released from soil, plants, microorganisms, pavement, and the atmosphere when weather conditions change.
Is petrichor the smell before or after rain?
It is most strongly associated with rain contacting dry ground. You may smell it beforehand when rain is already falling nearby and storm winds carry the aerosols toward your still-dry location.
Why does the first rain after a dry spell smell strongest?
Dry conditions allow scent-producing material to accumulate on surfaces. The first drops release and aerosolize that concentrated mixture; later rainfall may wash much of it away.
Can the smell of rain accurately predict a storm?
It can be a genuine local clue, but it is not a reliable substitute for radar, forecasts, or official warnings. Wind can carry odors from rain that never reaches your exact location, and not every storm produces a noticeable scent.
A small weather clue with a big scientific story
Smelling rain before it falls is not supernatural. It is an elegant example of chemistry, microbiology, fluid dynamics, weather, and human perception working together. A faint scent can reveal that droplets are already striking soil somewhere upwind, that storm air is descending, or that moisture is releasing compounds held by the landscape.
The next time an earthy note appears beneath a darkening sky, pause for a moment. Your nose may be detecting a chain of events that began in microscopic soil communities and traveled on the wind before the rain itself arrived.
Explore more curious science at Bing QuizzesSources and further reading
- CSIRO, “The smell of rain: how our scientists invented a new word,” summarizing Bear and Thomas’s 1964 Nature paper on petrichor. Read the CSIRO overview and view the original paper record.
- Joung, Y. S., and Buie, C. R. “Aerosol generation by raindrop impact on soil.” Nature Communications 6, 6083 (2015). View the study.
- UK Met Office, “Rain,” including the release of petrichor-related aerosols from soil. Read the explainer.
- Scientific American, “Storm Scents: It’s True, You Can Smell Oncoming Summer Rain,” on storm downdrafts, ozone, and petrichor. Read the article.
- American Chemical Society, “Geosmin,” Molecule of the Week. Read the chemical profile.
- Trimmer, C. et al. “Genetic variation across the human olfactory receptor repertoire alters odor perception.” Proceedings of the National Academy of Sciences (2019). View the study.
- RSPCA, guidance on dogs and their highly developed senses. Read the overview.