Why does a persons nose run when they are cold?

Answer 1

As we breathe, warm air exits our lungs and warms the membranes inside our noses. After we exhale, we then inhale another breath of cold air. The cold air comes into contact with the warmer areas inside out nostrils and minute droplets of moisture held by the cold air are deposited onto the hairs and membranes of our noses. Eventually, enough fluid builds up and it starts to run out of our noses.
The same thing happens to the inside of the car windows when the car is warm inside and it is cold outside.

Answer 2

your nose runs because of the moisture in your breath. As your breath exits, the moisture condenses due to the cold and it collects on your nose hairs and the inside of your nose, and as it collects, it has to run somewhere.

Answer 3

The mucus in the nose can't work as well in cold weather hence the runny nose!