Heat Index vs. Wet Bulb Globe Temperature (WBGT)


Heat Index vs. Wet Bulb Globe Temperature (WBGT)

Jul 13, 2023
Colin Perry

You’ve been hearing a lot about it recently, and Wet Bulb Globe Temperature (WBGT) may be something completely new for you. I don’t blame you, even in 2024, it’s far underutilized in a lot of organizations’ weather monitoring. Part of this is due to the fact that Heat Index is still very popular and more widely known. But we can do better, WBGT is by far and large the better metric for heat stress on the body outdoors.

What is Wet Bulb Globe Temperature (WBGT)?

WBGT in a nutshell is a more in-depth metric taking into account more of the environment (Direct sunlight, water vapor capacity, cloud coverage, etc.).

Because of this, wet bulb globe temperature (WBGT) is the best metric to use to calculate and monitor heat stress on the human body.

While WBGT calculators exist online, realtime, trusted WBGT meters and software should be used in order to ensure proper heat safety management.

What is Heat Index?

Heat Index, aka “Humiture”, takes into account temperature and humidity, straightforward and simple!

According to Weather.gov, “The heat index, also known as the apparent temperature, is what the temperature feels like to the human body when relative humidity is combined with the air temperature.”

While Heat Index has been used for many years, it’s not always sufficient to use this metric. That’s where WBGT comes in!

Heat Index
Measured in the sun
Measured in the shade
Uses temperature
Uses relative humidity
Uses wind
Uses cloud cover
Uses sun angle

Heat Index VS WBGT Comparison

Here are some side by side examples of WBGT and Heat Index:

Temp FDwpt FRH %Sky %Wind MPHHeatIdx FWBGT F
(chart from Weather.gov)

WBGT vs. heat index: similarities

Let us find some common ground real quick. Both WBGT and Heat Index aim to fulfill the same purpose, measuring heat stress of the environment on the human body. Additionally, they share some similar variables as well, essentially both taking into account ambient temperature and humidity. However, that’s where the similarities end.

Where and when should these different heat metrics be used?

WBGT, where used wisely, far outperforms Heat index in accuracy, but where do we use it? The great outdoors! WBGT is used best outside of any building, athletic center, or any area that is climate controlled. Simple as that, any area outside in direct sunlight is where this index shines bright, so to say.

Heat index, on the other hand, is essentially used in the opposite environment. This measurement is best used within any building, athletic center, environment that is not climate controlled and is out of direct sunlight. This could be an old gym without A/C, large covered athletic complex, construction site that does not have proper ventilation/air movement through it, anything that does not involve direct sunlight.

For example, WBGT should be used to help prepare and monitor outdoor activities safely. If WBGT is expected to be high, athletes, workers, and other individuals who will be spending time outside should be prepared with lightweight clothing, hats, and should plan to take frequent breaks in the shade. It’s also important to drink plenty of water when the WBGT is high.

WBGT for better heat stress management and safety

To be blunt, having a more accurate metric for heat stress allows for better preparedness in extreme environmental conditions. Think of it this way, if you are responsible for the safety of hundreds, if not thousands of people, are you going to want something that’s “close enough” or do you want the best and most accurate product in the field?

There are plenty of government agencies that use this index, in addition to plenty of organizations and Academic/Athletic institutions. This includes the U.S. Military, the American Conference of Governmental Industrial Hygienists, American College of Sports Medicine, National Weather Service, OSHA, and countless Universities. Although this tool has been well established for years, many people are still just now finding out about it. Every day, more and more people are catching up to the standards of environmental weather monitoring.

Perry Weather’s real time weather software allows organizations to easily track the heat index and wet bulb globe temperature, as well as other crucial weather metrics in real time. Learn more about our software today and even sign up for a free trial!

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