Hot and heavy; facts about humidity - WNEM TV 5

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Hot and heavy; facts about humidity

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How the dew point will make things feel outside. How the dew point will make things feel outside.
(Source: WNEM) (Source: WNEM)

Hot, humid, sticky, muggy, heavy, thick, and suffocating.

These are all words many used to describe humid air. The question is do you know what humidity actually is, or that humid air is actually lighter than dry air? Here are the facts about humidity! 

Relative Humidity is Pointless (Usually):

While relative humidity is useful for dry air situations and predicting the risk for fires, it is not very useful to tell you how humid it will feel outside. The vast majority of the time the relative humidity values will reach to or near 100% at night and drop during the day. That is because relative humidity is a percentage based on moisture in the air and how much moisture could be in the air. There is an equation to demonstrate all of this, but I will spare you the details. 

Take Friday's forecast as an example. The high will be around 87 with a dew point near 70. That gives us a relative humidity of only 57%. Doesn't sound bad, but trust me it is going to feel very muggy and uncomfortable outside. 

What is Dew Point?:

Dew point is the temperature that the air would need to reach for dew to form on your lawn. If the dew point and the temperature are the same, that also means the relative humidity will be 100%. These numbers are much more useful to tell you what to expect outside in terms of the humidity, as they relate directly to how the air will feel as you go outside. 

In general a dew point temperature in the 50s or below will feel comfortable, 60 to 65 will feel a little humid, 65 to 70 will definitely feel humid, 70 to 75 will feel very humid, and anything over 75 will feel rather oppressive. 

How Can Humid Air be Lighter?:

There is always water in the air we breath, but when things get humid there is more of it. In order to get more water into the air, it has to push other elements, like nitrogen and oxygen, out of the way. Compared to those two gases, water vapor weighs less, making the new mixture lighter as a result. Basically, if you had two balloons, one filled with dry and one filled with moist air to the same amount, the balloon with dry air inside would weigh more. 

This means a lot for weather forecasting, as moist air is usually more unstable, meaning that it is more likely to rise into a thunderstorm. This is one of the main reasons those hot and humid summer afternoons will lead to scattered thunderstorms popping up around the region. 

So Why Does it Feel Heavier?:

Simply put, your lungs have a hard time breathing air with more moisture in it. It feels heavy because your lungs have to work harder to get the oxygen you need to function. 

So now that you know a little more about humidity, and with humid and hot conditions in the forecast, take it easy, stay cool, and be sure to kick the AC on to make things more comfortable on these sticky summer afternoons. 

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