For most of the US, autumn is also characterized by lower temperatures and less humidity. “Cooler air holds fewer molecules, meaning fewer things are floating around for our noses to detect—the air is less ‘cluttered’ than during warmer, more humid seasons,” Dr. Crimmins says. This all accounts for the “crisp, clean” feeling and aroma we attribute to fall air, she adds. But while nature plays a role, it’s not necessarily the odor of decaying leaves or lower humidity that we enjoy and remember so vividly—it’s all the sensations that come with those changes.

— Read more in The Scientific Reason Why the Smell of Autumn Makes You So Emotional at Self.

Cathrine Jansson-Boyd, a professor of consumer psychology at Anglia Ruskin University in the UK, connects the shift away from a signature scent with a weakening sense of identity. "The more time you spend online, the more you want to change how you represent yourself," she says. "You never really establish a proper sense of self."

— Read more in Smells like teen spirit: Inside Gen Z's obsession with luxury fragrances at Business Insider.