You step outside on a winter day, and the air smells crisp, clean, and a bit woodsy. It’s not your imagination. The air actually does smell fresher in winter. What are you smelling? Does it have to do with the chilly temperatures, or is it because indoor air is so stuffy this time of year that stepping into an arctic blast feels good? Outdoor air starts to smell cleaner as the temperatures dip into the 30s. That classic winter-air scent comes from what we’re smelling and what we’re not smelling. In winter, the humidity levels drop, and that’s a treat for your nose. The reason it smells better in winter is because in summertime high pressure is over an area for an extended period of time. That high-pressure air just sits there, where pollutants can get trapped. Low pressure and humidity that come with winter have less of a funk. You can detect terpenes — naturally fragrant compounds in pines and other plants. That scent is often perceived as cozy or nostalgic. From December to February, most plants are dormant, making evergreen notes stand out even more, giving the cold air that Christmas-tree smell. There’s also a psychological component that goes beyond smelling. Crisp air signals a brain reset, making us feel alert. Maybe that’s why we feel happier when we get outdoors on a bright and chilly winter day.
