why is there steam when you breath by your mouth in a cold day??

Answer 1

Because the air outside is cold and the air in your lungs is warm. When you exhale the warm air collides with the cold air and forms condensation. It's similar to fog. The warmer air in the lower elevations collides with the cooler air in the higher elevations and causes the fog you see when going up the mountain. Hot air rises and cool air sinks and they collide forming fog.

Answer 2

WEll it's b/c the hot and cold air mix and make it!