Wet Bulb Globe Temperature, or WBGT, is your body’s true heat stress scorecard.
Unlike the heat index, which only considers temperature and humidity, calculating WBGT factors in the sun’s intensity, wind, and cloud cover. Think of it as a supercharged weather report designed to keep you safe.
Whether you’re an athletic trainer or organizing an outdoor event, knowing how to calculate wet bulb globe temperature can be a game-changer for heat safety.
Simple Outdoor WBGT Calculator
Our outdoor WBGT calculator helps you automatically measure the wet bulb globe temperature quickly and efficiently without any complicated input.
Calculating WBGT isn’t just for the weather geeks—it’s essential for anyone who spends time outdoors in the heat.
Whether you’re using a WBGT calculator or crunching the numbers yourself, understanding this metric can help you dodge heat-related illnesses and keep your cool, no matter how hot it gets!
This blog breaks down how to calculate WBGT and shows why calculating WBGT measurement is the key to keeping cool.
What is Wet Bulb Globe Temperature (WBGT)?
Wet bulb globe temperature (WBGT) is a measure of how direct sunlight truly feels to the human body, factoring in multiple environmental elements to gauge heat stress.
WBGT readings, unlike regular temperature readings, combine the effects of:
- Air temperature and air movement
- Relative humidity
- Radiant heat or Sun angle
- Cloud cover (solar radiation)
According to the National Weather Service, WBGT is a better metric if you work or exercise in direct sunlight.
To effectively manage heat exposure, it’s crucial to grasp the components and methods behind calculating WBGT. This understanding is essential whether you use a dedicated WBGT calculator, convert from dry bulb to wet bulb temperature, or perform the WBGT calculations by hand.
How Do You Measure the WBGT Index?
To calculate the Wet Bulb Globe Temperature (WBGT) in fahrenheit, the following formula is used:
WBGT = (0.7 * Tw) + (0.2 * Tg) + (0.1 * T)
In this WBGT formula, there are three important variables to note:
- T = Temperature in Celsius
- Tg = Globe Thermometer Temperature (in Celsius) – this is measured by a thermometer placed in a special black globe to estimate solar radiation without the effects of the light itself
- Tw = Wet-bulb Temperature (in Celsius)
But you don’t need to memorize this. Perry Weather takes care of wet bulb temperature calculation for you!
Why Wet Bulb Globe Temperature (WBGT) Matters
Wet bulb globe temperature helps in maintaining a proper workload in direct sunlight as well as deterring heat strokes during an excessive heat warning.
This is especially important as it differs from the heat index, which only accounts for temperature and humidity in its calculation for shaded areas.
For instance, if the WBGT is below 80, no extra precautions are necessary. But if the wet bulb globe temperature is between 80-90, the body will stress within 20-45 minutes of work or exercise in direct sunlight, with the time until stress becoming shorter as the wet-bulb globe temperature increases.
If the WBGT is above 90, the body will stress in just 15 minutes and it is crucial to drink plenty of fluids and take very frequent breaks in the shade.
Why do I need to monitor WBGT?
WBGT thermometers have been growing in popularity and usefulness, especially for youth sports and athletic programs.
States like Georgia have begun mandating the use and monitoring of WBGT for all high school outdoor athletic programs. The University Interscholastic League (UIL) has recommended Texas athletic programs to start using WBGT and moving away from heat index.
When schools and organizations follow wet bulb weather and its guidelines, they can make better decisions about:
- when it’s safe to be outside practicing
- hydration and how often to take water breaks
- whether to use pads during practices
- if they should cancel practice and physical activity
- if they should move practice or the event indoors
Read more about monitoring WBGT here.
Why Use WBGT to Calculate Heat Stress?
- It’s Apt for Outdoor Activity: Since WBGT is a measure of heat-related stress specifically, it is an important factor to consider anytime people are performing some kind of outdoor activity, and for calculating work/rest schedules.
To ensure the safety of working conditions, regulations are in place for WBGT monitoring, making it essential to calculate WBGT accurately.
- WBGT is Highly Valuable for High School and Collegiate Athletics: WBGT is also highly valuable information for high school and collegiate athletics, event venues, OSHA regulated construction, city sports leagues, and military training facilities. The applications are endless.
For example, during a high school football practice, kids are training their hearts out in the heat of August. Knowing the wet bulb globe temperature can ensure that players in direct sunlight will not put a dangerous amount of stress on their bodies, as well as help the coaches know how often they can take breaks and need hydration.
- WBGT can even show you when humidity decreases: A humidity decrease generally causes a rise in temperature, which is perfect for snowmakers. Therefore, being able to calculate WBGT is also beneficial for winter sports and activities.
What is Wet Bulb Temperature?
When water evaporates into the air it creates a cooling effect, but the amount of this cooling varies depending on the overall air temperature and the relative humidity.
Wet-bulb temperature measures how cool the air can become through water evaporation. It’s influenced by both temperature and humidity. Essentially, it reflects the body’s ability to cool itself through sweating.
Here is the equation for wet bulb temperature:
This is a rather complex WBGT formula:
Tw = T * arctan[0.151977 * (rh% + 8.313659)^(1/2)] + arctan(T + rh%) – arctan(rh% – 1.676331) + 0.00391838 *(rh%)^(3/2) * arctan(0.023101 * rh%) – 4.686035
Here, “T” is the temperature in celsius, and “rh” represents the relative humidity.
With this final calculation, you can calculate WBGT completely.
Learn more about the differences between wet bulb temperature and wet bulb globe temperature here.
Best Ways to Calculate WBGT
Option 1: Calculate WBGT by Hand
(.07 * Wet-bulb Temp) + (0.2 * Globe Thermometer Temp) + (0.1 * Temperature) = Wet Bulb Globe Temperature
Option 2: Weather Apps
Pros:
– Convenient and easy to use
Cons:
– Only hourly updates. A lot can change in an hour
– No site-specific data. Pulls data from the National Weather Service, which could be up to 25 miles away.
– Often shows inaccurate measurements.
Option 3: Handheld WBGT Devices
Pros:
– Portable
– Durable; Built for outdoors
Cons:
– Too manual: Lacks automated WBGT data logging features
– Inaccurate readings: Small black bulb sensor causes massive spikes in WBGT readings
– Lacks radiation shield, leading to erroneously high WBGT readings
Okay, that was a lot. But don’t panic!
You don’t really need a WBGT calculator or a formula to calculate the WBGT accurately. There are much faster and much, much easier ways to calculate wet bulb globe temperature.
Option 4: Perry Weather
For regular users of wet bulb globe temperature calculations and regulations, it’s best to use an integrated WBGT calculator service or a WBGT device for up-to-date information.
Perry Weather offers weather monitoring software and hardware to simplify the entire WBGT monitoring process.
Learn more about how Perry Weather tracks the wet bulb globe temperature and how it can help you here
Watch how our customers use Perry Weather to calculate WBGT
Watch more customer stories here
How Do I Calculate the Wet Bulb Globe Temperature (WBGT)?
The wet bulb globe temperature (WBGT) can be measured with on-site weather stations, handheld devices known as WBGT monitors, or online WBGT and weather monitoring apps.
These tools calculate the temperature, humidity, and sunlight to compute the WBGT index.
How can I take a WBGT reading?
Wet bulb globe temperature readings can be taken using a WBGT monitoring device like a weather monitoring station or a handheld monitor. Readings must be taken by an athletic director/administrator or medical personnel overseeing the event.
The WBGT should be monitored throughout the event and readings must be taken every 20 to 30 minutes, with athletic activities being adjusted accordingly.
Participation modifications must be communicated to the coaching staff before and during practice.
Why Should I Track the WBGT?
Regularly monitoring the WBGT levels allows coaches and athletic trainers to adjust training schedules, implement hydration protocols, and make informed decisions to protect athletes from high temperature and heat-related risks.
Tracking the WBGT is crucial to protect athletes’ health and safety during outdoor practices, games, and events.
How often should we track WBGT?
WBGT should be measured regularly, especially during periods of high heat or physical activity. The frequency depends on the specific situation and guidelines.
Can I calculate WBGT using a smartphone app?
While some apps provide estimates of WBGT, WBGT monitors and weather stations like Perry Weather offer more accurate and reliable measurements.
Are heat index and wet bulb globe temperature the same?
No. WBGT is best used outside any building, athletic center, or any area that is climate controlled. Heat index, on the other hand, is best used within any building, athletic center, and casual, shaded environments. Learn more here.
Perry Weather is your partner in weather tracking and how to measure wet bulb, going beyond a simple wet bulb and dry bulb calculator.
The streamlined approach uses the latest technology to provide a multitude of industries with real-time updates to temperature, relative humidity, wet bulb temperature, globe thermometer temperature, and WBGT.
Using Perry Weather Weather Station software, you don’t need a manual WBGT calculator or WBGT meter and it only takes the click of a button to receive consistently calculated wet bulb globe temperatures no matter where you are and ensure your people are safe in every job, every game, and every season. Sign up for a free trial and see Perry Weather in action for yourself!
