Should I use Wet Bulb or Wet Bulb Globe Temperature (WBGT)?


Should I use Wet Bulb or Wet Bulb Globe Temperature (WBGT)?

Aug 24, 2021
Colin Perry

Don’t mistake wet bulb for wet bulb globe temperature (WBGT). They are different measurements, but are often – and mistakenly – used interchangeably.

What’s the difference between wet bulb and WBGT?

Think of wet bulb globe temperature (WBGT) as the new, better heat index or “feels like” temperature. It more holistically measures heat stress on the body by answering: how efficiently can your body produce sweat to cool itself down?

WBGT considers a few factors: wind speed, sun angle, cloud cover, and wet bulb temperature (temperature and relative humidity). Wet bulb temperature is not WBGT, but it is a factor in the WBGT calculation.

Wet bulb temperature (“wet bulb” for short) represents the lowest temperature that air can reach through water evaporation alone. It is measured by covering a temperature sensor with a wet cloth. Think of a wet bathing suit – the dry air causes the water to evaporate and release heat, making you feel cold.

So, which one should I use: wet bulb, or wet bulb globe temperature?

If you are concerned with heat stress for outdoor activity, you should almost certainly use wet bulb globe temperature (WBGT) as your measurement. School athletics (K-12), collegiate athletics, construction, and other outdoor industries commonly use WBGT. If you are an athletic trainer, athletic director, or coach, you know how excessive heat can impact your student athletes.

If you hear someone mention “wet bulb” in the context of heat, they are probably talking about WBGT.

On the other hand, wet bulb temperature – not WBGT – is more frequently associated with cold-related activities, such as snowmaking and cooling towers.

… But what about “heat index”?

Wet bulb globe temperature (WBGT) serves a similar purpose as heat index – measuring heat stress on the human body – but provides a significantly improved, more accurate measurement than a simple heat index (“feels like” temperature).

Got it. How do I find the current WBGT?

An on-site sensor provides the most accurate and real-time measurement of WBGT. Unless you have an on-site sensor, any apps or websites providing WBGT are simply using a calculated estimate, which can significantly deviate from the actual WBGT.

Perry Weather is the leading weather safety platform for organizations keeping their teams safe in the midst of excessive heat and other environmental conditions. Learn more about how we can help your organization adequately monitor WBGT.

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