system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does being really cold tend to make your nose run?
gpt
Cold air is less humid. The cold dry air dries out your nose and airway. Your body produces increased mucus to compensate and keep your airway from drying up. Also the water vapour that you exhale from your lungs condenses in the cold airway of your nose and makes your nose run.