You might have noticed cloud of air outside your mouth when you talk, yawn or just breathe out during cold winters.Our breath is very much noticeable when the outside temperature is below 10 degree Celsius, but not on sunny days.
You must be familiar with the respiratory process of our body. We inhale oxygen from outside air and breathe out carbon dioxide. Along with carbon dioxide, we do exhale some amount of moisture (water vapor). It is because of this moisture content in our breath we see the cloud of air in winter.
During winter, the outside temperature drops. When we walk outside on such a day, the moisture that we exhale gets in contact with the cold air outside. Now our breath coming from inside our body is warm compared to the outside air. When some water vapor in warm air comes in contact with lot of cold air, it starts to condense into water droplets. You may also be aware that cold air cannot hold as much water vapor as warm air. These water droplets actually appear to be the little cloud of air that we see.
It is clear the cloud of air doesn’t appear on a sunny day because the outside air is warm and it can hold more water vapor.