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.