What Is Wet Bulb Temperature? The Weather Term You’ll Hear More This Summer

It's time once again to learn a new weather term. If you are a fellow weather nerd, you've probably been hearing this pop up over the last few years, especially if you were in the military or played sports. And this year, I'm seeing it more and more in news stories. That means it's going mainstream and we're going to be hearing it more.

This new weather term is 'wet bulb.' As in wet bulb temperature. It has to do with extreme heat, and if you hear it used in your local forecast, that means things are about to get serious.

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What Does 'Wet Bulb Temperature' Actually Mean?

The full term is 'Wet Bulb Globe Temperature,' and it has to do with extreme heat.

The National Weather Service says, " The Wet Bulb Globe Temperature (WBGT) is an indicator of heat related stress on the human body at work (or play) in direct sunlight. It takes into account multiple atmospheric variables, including: temperature, humidity, wind speed, sun angle, and cloud cover."

The wet bulb temperature is similar to the heat index, which is the temperature combined with the relative humidity. When you hear the weatherperson say something like, "It's 95 but feels like 102," that means that the moisture in the air, humidity, is combining with the air temperature to make things that much hotter for the human body. Heat index is sort of the summer cousin to winter's wind chill.

The wet bulb measurement takes more factors into account when calculating the temperature and how our bodies react. In addition to the humidity, it considers wind, cloud cover, and the sun's angle.

How Our Bodies React to High Wet Bulb Readings

For people, the wet bulb temperature is an indicator of heat stress on our bodies. We cool ourselves by sweating, we get ourselves all wet, and count on the air around us to evaporate that moisture, which cools our bodies.

That's why a really humid day sucks so much. Becuse the air is already full of mostiture, it's harder for that air to suck up the moisture, sweat, our bodies produce. And we don't cool down as effectively.

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If you've ever worked or played sports in high-humidity environments, like Sioux Falls sometimes experiences, and then done it in a dryer climate, like in Rapid City, you know how miserable humidity makes things.

All that to say, that when you hear the weather talking about the wet bulb temperature, just know that it's going to be hot and gross outside. The hotter it gets, the less your body will be able to cool itself down.

Where the Term ‘Wet Bulb’ Comes From

The term 'wet bulb' comes from the way the temperature is measured, using three different thermometers. One measures the sun and cloud cover, one measures the air temperature, and the other measures the humidity.