It’s a chilly fall morning as you head outside to grab the mail, but wait… you can see your breath! That’s how you know winter is right around the corner and cold weather is coming. Have you ever wondered why you can see your breath in these chilly temperatures? It’s a simple answer: water.
While many attribute the visible breath solely to falling temperatures, the amount of moisture in the atmosphere is just as important. The perfect combination of temperature and humidity is actually the cause of the age-old phenomenon.
The Science Behind It All
The human body is made up of nearly 70 percent water, which causes the air in our lungs to be almost completely saturated in water vapor, which is water in its gas form. This water vapor is the same temperature as our bodies, 98.6 degrees Fahrenheit. Cold air can’t hold as much moisture as warm air, which is often why cold winter days feel so dry and hot summer days are thick with humidity.
When you exhale a breath filled with the warm air from your lungs, it enters the cold atmosphere of a winter day. The cold air immediately lowers the temperature of our breath and briefly reaches a dew point. A dew point is the exact temperature the air needs to be at to achieve humidity.
Air cannot hold water vapor at dew point, causing the gas to turn to liquid form, or water vapor to water. This is the process of condensation and what makes up that little foggy cloud we see in the cold. The transformation of gas to liquid creates miniscule water droplets visible to the human eye.
This is a great way to visualize exactly how far things travel when you’re simply breathing and speaking. These tiny water molecules in your breath spread just as easily in every type of weather. All the more reason to wear a mask to prevent spreading germs!
Just How Cold Does it Have to Be?
There is no exact temperature in which condensation is guaranteed to occur. As we know, the relative humidity in the air is a contributing environmental factor that goes into the equation of visible breath. However, when the temperature falls below 45 degrees Fahrenheit, there’s a good chance you’ll be able to see your breath.
Now the next time you see your breath on a cold day, you’ll know you’re seeing the process of condensation in action.