Have you ever noticed that you can tell when – with all due respect to Game of Thrones – winter is coming? Imagine stepping outside on a cold winter day and inhaling deeply. Your surroundings do indeed smell different than they smell in warmer months, and it’s not your imagination. Describing what winter smells like is somewhat ineffable, but perhaps it’s the scent of colder earth, snow, or chimney smoke.

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Scents of all kinds are affected by temperature. One way to think of it is to consider a plate of leftovers kept in the refrigerator. If you were to take a whiff of your leftover meal before heating, you may notice some of the foods’ unique scent, but it wouldn’t be very powerful. Now heat the food up, and smell it again. You’ll notice that the scent is much more distinctive now that it’s warm.

You’ve probably figured out that the smell of cannabis smoke seems less funky when it’s cold outside as well (making it easier to avoid your pot-hating uncle during the holidays) and there are a couple of reasons for that. But first, let’s take a look at how our sense of smell works.

The Sense of Smell

In the back of the nose are millions of sensory neurons in a strip of tissue called the olfactory epithelium, where about 450 olfactory receptors reside, and these receptors bind to odor molecules. Once an odor molecule binds with an olfactory receptor, it sends a signal to the olfactory bulb, which sends this signal to the brain for processing.

Labelled diagram of the anatomy of the human face showing a side profile dissection Olfactory nerves would be found in this area (a.) in the nasal cavity as the olfactory bulb is present above the cribriform plate (D.). photo credit
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From there, it heads to the piriform cortex to identify the smell. Next, it heads to the thalamus, then the orbitofrontal cortex where it combines with taste information. This coupling explains why, when you have a cold for example, it is harder to appreciate the taste and scent of food.

Smell is also inextricably linked to memory and emotion. If you’ve ever been shot down memory lane when a stranger walks by wearing the signature scent of your ex, or the scent of pumpkin pie conjures up memories of grandma, that’s the thalamus at work, sending scent information to the hippocampus and amygdala, involved in learning and memory.

Warmer Weather is Accentuated

Scent molecules are much more active and move more quickly when the outside temperature is warmer, making the scent more pungent. But, when the weather outside is cold, these odor-carrying molecules move much more slowly. Thus, a scent like curbside garbage that might knock you out on a hot and humid summer day is tolerable when it’s cooler.

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Another reason why weed smells less pungent in the cooler months is because the olfactory receptors in our noses tend to go into semi-hibernation, making us less sensitive to smell. Researchers believe this is a protective response, to protect the nose from cold, dry air.

With odor molecules moving more slowly and the olfactory sensors retreating in cooler months, the scent of weed indeed smells less like its funky self.