Wet Bulb Globe Temperature: The Superior Metric for Endurance Sports

Published July 19, 2023

Wet Bulb Globe Temperature: The Superior Metric for Endurance Sports Header Image

When it comes to endurance sports, understanding the environmental conditions is crucial for athlete safety and optimal performance. Heat-related illnesses, such as heat stroke and heat exhaustion, pose significant risks to athletes, making it essential to measure and monitor the thermal environment accurately. While both Wet Bulb Globe Temperature (WBGT) and Heat Index are metrics used to assess the impact of heat on the human body, this blog post will explain why WBGT stands out as the superior metric for endurance sports.

Understanding Wet Bulb Globe Temperature

WBGT is a composite index that considers several environmental factors, including air temperature, humidity, wind speed, and solar radiation. It offers a more comprehensive assessment of heat stress as it considers the combined effect of these elements on the human body. The formula for calculating WBGT is as follows:

WBGT Formula

The Wet Bulb Temperature reflects the combined effect of air temperature and humidity, while the Globe Temperature accounts for radiant heat from the sun and other sources.

Heat Index: A Limited Perspective

Heat Index, on the other hand, is a simpler metric that only considers air temperature and humidity. It is calculated based on how the temperature feels to the human body and is often used as a general guide for heat-related precautions. The formula for Heat Index is as follows:

Heat Index Formula

Though Heat Index provides some insights into how hot it feels, it fails to consider other crucial elements, such as wind speed and radiant heat, which are significant contributors to heat stress in endurance sports.

Why WBGT is Better for Endurance Sports

Comprehensive Assessment

WBGT provides a more comprehensive and accurate evaluation of the thermal environment, giving athletes and event organizers a clearer picture of the potential risks. By considering air temperature, humidity, wind speed, and radiant heat, WBGT gives a holistic view of the heat stress experienced by athletes.

Risk Identification and Safety

Endurance sports demand rigorous physical exertion for extended periods, making athletes susceptible to heat-related illnesses. WBGT’s ability to assess various heat stress factors allows for early identification of potential risks, enabling athletes and event organizers to take the necessary precautions to ensure safety and prevent heat-related injuries.

Tailored Recommendations

Due to its holistic approach, WBGT provides specific guidelines for different activity levels and heat stress categories. This means that athletes can adjust their training or competition strategies based on the current environmental conditions, optimizing their performance while minimizing health risks.

WBGT Table

Compliance with Safety Standards

Many sports organizations and governing bodies use WBGT as the standard metric for determining whether it is safe to conduct outdoor events. By adopting WBGT as the primary heat stress metric, endurance sports events adhere to globally recognized safety guidelines, fostering a culture of athlete well-being.


While Heat Index has been commonly used to gauge the impact of heat on the human body, it falls short of providing a comprehensive assessment of heat stress for endurance sports. Wet Bulb Globe Temperature (WBGT) emerges as the superior metric due to its consideration of multiple environmental factors, thereby offering a more accurate evaluation of heat stress and better guidelines for athlete safety and performance. By prioritizing the use of WBGT, endurance sports can elevate the well-being of athletes and create an environment where optimal performance and safety go hand in hand.

How is WBGT used in Apollo Weather?

  1. Every hourly forecast includes WBGT measurements
  2. Users have the option of choosing “Wet Bulb” as the temperature method in their Ideal Conditions
  3. Hourly ratings show Perfect, Acceptable or Bad conditions using WBGT instead of Actual and Feels Like temperatures

You can download Apollo Weather from the App Store.

Apollo Weather

Apollo is the best weather app for runners, cyclists and other endurance athletes who want to train under the best conditions possible.

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