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It’s Not the Heat, It’s the Humidity

27 Jul 2017, 8:20 am

“It’s not the heat, it’s the humidity.”
–Any Person in Summer

If you live somewhere with even a drop of moisture in the air, this old adage is probably a bit played-out.
But before you go ahead and write it off as just another hot day, let me explain why this little quip might just save your life.

What is Humidity?

Humidity is simply the amount of water vapor in the air.

Even though you can’t see it, there are always tiny little water droplets suspended in the atmosphere. Those little droplets do wonders when it comes to affecting the weather, but we are just going to focus on how those little droplets up the danger of summer-time heat waves.

Dew Point 

There are many different ways of expressing humidity, but for simplicity sake we are just going to focus on the dew point as a means of measuring water content in the air.

Dew point is the temperature at which the air becomes completely saturated with water vapor.
Confusing right?
Right. So let’s break it down in a way that’s a little easier to understand.

The temperature can never drop below the dew point. And conversely, the dew point can never be higher than the temperature.
Knowing that little tid bit helps us explain that warmer air holds more moisture.

So as temperatures climb, it makes sense that we see higher dew points.

As far as what dew points mean, here’s a neat little table to help break it down:

But Why Does it Make Heat Worse?

If humidity is something you battle every summer, then you are familiar with the heat index.

Heat index is the summer-time version of wind chill in the winter. It’s the temperature that it feels to our bodies. So when you add the humidity to the temperature (in the most complicated math equation of simple weather) you get the temperature that your body thinks it is in the heat.

To save you the pain of the math, here’s a little table from NOAA breaking down the affect of humidity on heat and your body.

The reason it feels so much hotter outside is because the extra bit of moisture in the air inhibits the ability of sweat to cool you down.

You see, your body is a fantastic machine. As you sweat, the tiny little droplets of water evaporate from your skin– acting to cool or regulate your body’s temperature.

The moisture in the air or humidity keeps the sweat from evaporating off your skin. So that inability of your body to naturally regulate its temperature means it actually feels warmer outside!

Dry Heat

At some point it gets hot enough that the presence of humidity doesn’t matter.

Don’t believe me?
Just ask any resident of the desert southwest during meteorological summer.

Beat the Heat

If you’re looking to stay safe in the heat, here’s some light reading on what you need to know to avoid heat stroke.

Exercising in Excessive Heat

For WeatherNation — Meteorologist Jeremy LaGoo

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