MUNDANE MYSTERIES: How Do We “Smell” Snow?

Does snow have a scent? Your initial response might be “no”, since snow is only frozen water, which should be odorless. But, if you’ve ever predicted a big snowstorm based on a familiar tickle in your nose, then you understand the answer isn’t straightforward. So, what exactly happens when we “smell” snow?

The answer has less to do with specific odor molecules as it does with the climate. There’s a perfect storm of physical conditions needed to be able to smell snow. When temperatures near freezing right before it snows, it’s actually harder to detect scents in the air than it is during milder weather. Cold weather slows molecules in the air down. With less molecular activity, certain smells become less pungent. So, when “smelling snow”, you’re actually just smelling fewer other outdoor odors than what you’re used to.

But, if there was nothing else to it, a snowstorm would smell no different than a cold, dry day. The difference-maker? Humidity. The air is more humid than usual right before a snowstorm, which is what causes the flakes to fall: when the atmosphere hits its maximum amount of moisture, it dumps some of that wetness onto the ground in the form of rain, sleet, or, in our case, snow. That humidity also has the added effect of giving your sense of smell a quick boost. So, for many, the sensation of a warm, moist nose smelling certain elements in freezing weather ends up being linked with pending snowfall.

While all of that’s happening around you, there are systems at work inside your body that help to explain the unmistakable scent of snow. We sense the cold air we breath with our trigeminal nerve, which is the same nerve that interprets the sensations we get from tingly hot peppers or cool mint toothpaste, as well as other facial sensations that cause some folks to sneeze in sunlight. This is separate from our olfactory system, but we still lump that information with other more conventional scents like coffee or pine.

So, those elements (cold weather, humidity, and a stimulated trigeminal nerve) combine to create something that isn’t an odor, but a sensory experience we’ve come to associate with snow. Which is why, if you were to ask someone to describe the scent, they’d likely use words like “clean,” “fresh,” “cold”…all things that don’t have much of a scent at all.

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