At what temperature can you see your breath?
We all know that on a cold morning when you’re outside facing the elements, when exhaling your breath “shows.” In actuality, your breath is “showing” by forming a cloud. The same phenomenon happens from planes, with the air that exits the jet exhaust. Very warm and moist air from our mouth is exhaled and encounters very cold air, on contact with the cold air droplets, the moisture then condenses and forms tiny cloud droplets.
So why does this only happen when it’s cold? The main reason is because cold air cannot hold as much water vapor as warm air. By exhaling, we are overloading the cold air with water vapor, or giving it too much to hold. As a result, the droplets condense. The more moisture present in the air helps to make the likelihood of a tiny cloud to form. Also, light winds make for a better chance. When the winds are stronger, the air exhaled is more easily dispersed and carried to different locations, making condensation less likely.
While specific temperatures for this to occur are rather difficult to calculate, there is a “rule of thumb” temperature thrown around by some. It is believed that at about 45 degrees Fahrenheit and below, our breath tends to “show” when exhaling.