system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What exactly are we smelling when we smell that its going to snow?

I know i cant be alone in saying that i can always smell when its going to snow, especially the first snow/frost of the season. There's a distinct smell in the air that's just impossible to ignore. i was just wondering if anyone knew what exactly it is that causes that oh-so-nostalgic scent every winter.
gpt
Cold air holds less moisture. It's hard to smell things in cold, dry air. 

When the humidity rises, you feel it on your skin, and your nose can smell things better. The "smell of snow" is your heightened smell sensitivity thanks to humidity, despite the cold.