system
Given the following post, respond as if you're commenting on Reddit:
human
Why does my nose get all runny when it's cold outside?
gpt
Your nose serves two purposes: to warm and humidify the air.  When it is cold and dry outside, your nose works really hard to add moisture to the air coming in through your nose, however some times some of that fluid may start to run out of your nose.  Additionally, when breathing out through your nose, the warm and moist air from your body hits the cold air and causes the moisture to condense on the outside of your nose, further increasing the amount of fluid running out of your nose.