What Is Heavy Air?

The term "heavy air" is used often when discussing hot and humid weather. People say you can "cut the air with a knife," referring to its heaviness. However, the air people often refer to as heavy, isn't really the most moist type.

• Air

Misconceptions

• Humidity

  Heavy air is a term that people use when there is moisture in the air. This is called humidity. The more water that is contained in the air, the higher the humidity. The air feels heavy because it is thicker, making breathing harder. It also leaves moisture on your clothes and hair.

Identification

• Cool air is dry air.

  Actually, air weighs the most when it is cold and dry, even though it may not feel that way. Cold air is denser than humid air. Molecules are closer together when the air is cold, making air heavier.

Measure

• Higher pressure yields fairer days.

  The measure of weight in the air is called air pressure and it's measured with a barometer. As the air gets heavier, a barometer rises. This indicates that fair weather is here or on its way. When the air feels heavy, the barometer falls, indicating moisture in the air.

Cold Air

• An example of how heavy air is colder air can be found in most homes. When the air conditioner is running, the area closest to the floor is the coolest. Also, when you open your freezer, you can see the cold air rush out toward the floor.

Sea Level

• Air is heaviest at sea level.

  Air is the heaviest at sea level and gradually gets lighter the higher it gets. At the top of a mountain air is very thin and light. The atmosphere is made up of many levels of air and each one pushes down on the ones below.

Humidity

• Humidity is water vapor that is in the air. Relative humidity is the ratio of the actual water-vapor content of the air to its total capacity at the given temperature. Relative humidity is what weather forecasters usually refer to. The human body uses evaporation as a cooling mechanism and when it is humid, this is harder to do. This is another reason humidity is perceived as "heavy air" when it is actually not.