Why Can We See Our Breath in the Cold

Every time we go outside in the cold we can see our breath, it’s like making our own personal clouds and can be pretty satisfying to watch, but have we ever asked why can we see our breath in the cold? What causes this?

Temperature Differences Cause a Difference in Dew Point

The dew point is known as the point at which vapour, or in this case, our breath, begins to condense and form a liquid of sorts. When the air outside our lungs is warm as it is in summer, then it can hold more water before condensing it into a liquid. In colder times of the year, like winter, the air is colder and so can hold less water vapour, resulting in much less moisture in the air compared to summer.

Our Lungs are a Constant Temperature

Because we need to regulate a constant internal temperature in order to survive, our lungs are always warm and humid. When our breath leaves our lungs it is soaked with water vapour. If our breath hits cold air then it simply can’t hold as much vapour as the air form our lungs, so it condenses most of it which leaves them a liquid.

These condensed droplets attach themselves to tiny particles in our breath known as condensation nuclei, and can range from anything like dust to actual parts of our dead cells. So our breath in the cold follows the same laws as clouds do when they form in the air, it really is our own home-made cloud.