Hot conditions can create real risk, but they are still often judged by feel instead of being checked consistently. Heat stress happens when the body can no longer cool itself effectively, and that risk is shaped by more than just temperature. Humidity, radiant heat, and air movement all play a role. As heat risk becomes a bigger concern in both indoor and outdoor settings, heat stress monitoring gives users a clearer way to understand conditions and respond with confidence. 

Heat Index vs. WBGT: Two Common Ways to Measure Heat Stress 

Hot conditions can create real risk, but they are still often judged by feel instead of being checked consistently. Heat stress happens when the body can no longer cool itself effectively, and that risk is shaped by more than just temperature. Humidity, radiant heat, and air movement all play a role. As heat risk becomes a bigger concern in both indoor and outdoor settings, heat stress monitoring gives users a clearer way to understand conditions and respond with confidence. 

What is Heat Index? 

Heat Index is the simpler of the two approaches. It uses air temperature and relative humidity to show how hot conditions feel to people, which is why it is often called “Apparent Temperature”. In practice, Heat Index is useful when you want a fast, easy-to-understand check on how hot conditions feel. It works best in indoor settings or for basic screening.

What is WBGT (Wet Bulb Globe Temperature) 

WBGT is used to assess heat stress when conditions are shaped by more than just air temperature and humidity. Unlike the heat index, which works best in shaded or simpler conditions, WBGT is designed to give a more complete picture of how stressful the environment is on the body. It is especially useful when sun exposure, radiant heat, humidity, or other environmental factors add to the total heat load. 

WBGT is built from three core temperature inputs: wet-bulb, globe, and dry-bulb temperature. Together, these three measurements help show how much total heat load the environment is placing on the body. Wet-bulb temperature reflects the evaporative cooling side of heat stress. Globe temperature reflects radiant heat. Dry-bulb temperature represents the ambient air temperature. 

Because it captures more than just temperature and humidity, WBGT is especially useful in outdoor, industrial, and higher-risk environments 

How and Where Are Heat Stress Meters Used? 

Heat stress meters help answer one simple question: Are conditions becoming risky enough that action may be needed? Instead of relying only on how hot it feels, users can check conditions more consistently and respond based on actual measurements.  

In practice, they are commonly used for quick checks and ongoing monitoring. A reading might be taken before work starts, during the hottest part of the day, or repeatedly over the course of a shift, event, or activity period to see whether heat stress conditions are staying manageable or moving in the wrong direction.  

These meters are used in a wide range of settings, including outdoor worksites, hot indoor areas, and athletic environments.  

Different environments may call for different levels of heat stress assessment, from simple screening to a more complete view of total heat load. That practical approach also aligns with broader heat safety guidance from OSHA and NIOSH, which emphasizes monitoring, hydration, cool recovery areas, acclimatization, training, and worker observation.

Extech’s Approach to Heat Stress Monitoring 

Extech takes a practical approach to heat stress monitoring. Some users just need a simple way to check how hot conditions feel. Others need a broader view of heat stress in tougher environments. That is why the lineup includes options for basic Heat Index awareness, more complete WBGT assessment, and indoor heat and humidity monitoring—while keeping the focus on ease of use, balanced price and functionality, and tools that work well in real daily use. 

Explore Extech heat INDEX METERS and Heatwatch Stopwatch to find the right fit for your application