• Schools should use a scientifically proven device like a weather station or handheld device to monitor wet bulb globe temperature.
• Keep a record of these temperatures for all outdoors practices and wet blob reading should be taken every 30 minutes during practice for on site instruments. 
• Set them up 30 minutes before take readings, 15 minutes before the start and modify practice activity guidelines responsibly according to the wet ball globe temperature activity guidelines, when these things change, when you enter into different zones, as we see on the chart here. 
• All schools must have an emergency plan to prevent heat illnesses. The plan must include ways to cool athletes quickly on-site. This can be with cold water immersion tubs or tarps with ice. 
• The plan must also have cooling zones where the WBGT is 80°F or higher.
  

Learn more about the UIL heat safety recommendations here.

While both WBGT and Heat Index aim to measure how hot it feels outside, there are key differences in their calculations, how they work, and how they can help:

Heat Index: A Simplified Measure

The Heat index is also referred to as the feels like temperature, which really is just a calculation of air temperature and humidity. It tells us what the body feels the temperature outside is like. 

• Focuses on air temperature and humidity.
• Often referred to as the “feels like” temperature.
• Provides a basic estimate of heat stress.
• Measured in the shade, which can underestimate actual heat conditions.

WBGT: A More Holistic Measurement

The Wet bulb globe temperature (WBGT), on the other hand, is a much more holistic measurement. That’s why governing bodies like the UIL have started suggesting WBGT as the better heat stress metric. It takes into account not only air temperature, humidity but the angle of the sun. WBGT tells you how effective the body is at producing sweat, which is the main catalyst that cools yourself down. 

• Incorporates multiple factors: Considers air temperature, humidity, wind speed, sun angle, and cloud cover.
• Reflects body’s cooling ability: Measures how effectively the body can cool itself through sweat.
• Provides a more accurate picture: Offers a holistic view of heat stress, helping to prevent heat-related illnesses.
• Used by governing bodies: Organizations like the UIL recommend WBGT as the preferred heat stress metric.

Learn more about the differences between WBGT and the heat index here.

While handheld weather devices offer a degree of convenience, stationary weather stations provide significantly more accurate and reliable data for measuring heat stress.

Key Differences:

1. Size and Stability:
   • Stationary Weather Stations: Equipped with larger black bulb sensors that regulate temperature more consistently, mimicking how the human body would react to heat. These stations provide stable and accurate readings, less prone to rapid fluctuations.
   • Handheld Devices: Smaller sensors heat up and cool down quickly, leading to erratic readings. “We’ve seen it go from 94 degrees to 86 in minutes, which is almost impossible unless it’s pouring rain,” explains Colin Perry.
2. Sun Exposure and Accuracy:
   • Stationary Weather Stations: Designed with radiation shields that protect the temperature and humidity sensors from direct sunlight, ensuring consistent and accurate readings regardless of solar angle.
   • Handheld Devices: Lack of radiation shields can cause direct sunlight to affect readings, resulting in wild variations. “You might see 94°F one moment and something entirely different shortly after,” notes Perry.
3. Acclimation Time:
   • Stationary Weather Stations: Always positioned outdoors, these devices are acclimated to the environment, offering immediate and reliable data.
   • Handheld Devices: Need to be brought outside at least 45 minutes before readings to acclimate properly. As Josh Woodall shared, storing these devices in a climate-controlled area can lead to inconsistent readings when taken outside.
4. Convenience and Practicality:
   • Stationary Weather Stations: Provide real-time, visible data for all staff, reducing the need for manual setup and increasing trust. Coaches can see the data themselves without relying solely on trainers.
   • Handheld Devices: Require manual setup and consistent relocation, which can be a hassle, especially during early morning practices. “Am I going to go out at 4:30 AM to set this up?” asks Mike Hopper.

• Mike Hopper shares the practical benefit of stationary devices, noting, “It’s one less thing we have to worry about, especially during busy practice days.”

Understanding how different surfaces affect Wet Bulb Globe Temperature (WBGT) readings is crucial for accurate heat stress monitoring. When it comes to Wet Bulb Globe Temperature (WBGT) readings across different surfaces on your campus, the key takeaway is that the impact is generally negligible. 

Whether you’re dealing with synthetic turf, natural grass, or composite materials like tennis courts, the differences in WBGT readings are minimal. There’s no need for significant adjustments based on whether the activity is on turf or grass. You can follow the same heat safety protocols regardless of the surface.

Here’s why:

1. Scientific Studies: Two major studies from Dr. Grundstein at the University of Georgia found that WBGT readings across various surfaces—turf, grass, and composite courts—showed negligible differences. The air at athlete height (around 2 meters) mixes efficiently, evening out slight variations in temperature and humidity.
2. Surface Temperature vs. WBGT: While touching turf may feel hotter than grass, WBGT measurements are taken at head height where air is well-mixed. For instance, while turf might be slightly hotter and grass more humid, these differences blend together, making the overall WBGT readings nearly identical.
3. Real-World Example: Mike Hopper noted that while the surface temperature of turf can feel significantly hotter, like the 97°F he measured on concrete under a carport, the WBGT readings across different surfaces didn’t show a significant difference.
4. Height Adjustments: Perry Weather’s systems account for the height of the sensor placement. Whether it’s on a press box or a one-story building, the system adjusts the readings to match what would be expected at a 2-meter level, ensuring accurate WBGT readings across different surfaces. Colin notes that “The air mixes up very well and efficiently, making the end result negligible in terms of WBGT readings.”
5. Anecdotal Observations: Josh Woodall observed that grass areas, especially those watered frequently, might show slightly higher WBGT readings due to increased humidity, but these variations are typically small.

When you’re monitoring wet bulb globe temperature (WBGT) during a workout and the readings fluctuate between policy zones, it can be tricky to know how to respond. Here’s a detailed approach to handling these situations effectively:

1. Consistent Monitoring:
   • Continuously monitor the conditions throughout the workout. As Josh mentioned, “We’re monitoring conditions pretty consistently and not adjusting practices the moment something crosses into a new threshold.”
2. Stability Over Time:
   • Only make adjustments if the WBGT remains in a new zone for a consistent period. For example, if the temperature briefly spikes into a higher risk zone but then drops back down, you don’t need to change your workout plan immediately.
3. No Backward Adjustments:
   • Once you’ve adjusted for higher heat, don’t revert back to less restrictive practices even if the temperature falls. As Mikenoted, “We’ve already been out there for 30-45 minutes, and our core temperatures are already elevated.” Reverting could pose health risks.
4. Equipment Modifications:
   • Avoid making equipment changes (e.g., switching from pants to shorts) unless there’s a significant and sustained change in conditions. One example cited was that “nobody’s going to want to go back to the locker room to do that.”
5. Focus on Rest and Hydration:
   • Instead of adjusting gear, consider increasing the frequency of rest and water breaks. One participant advised, “Throw in an extra water break, throw in an extra rest.”
6. Use Practical Modifications:
   • Simple changes, like taking off helmets during non-active drills, can help manage heat exposure without major disruptions. As highlighted, “Take your helmets off during this warm-up drill, take your helmet off when you’re not actively in a drill.”
7. Game Plan:
   • Develop a pre-planned strategy with your coaches and athletic directors. As one speaker suggested, “Have a game plan and say we’re going to err on the side of caution.”
8. Err on the Side of Caution:
   • When in doubt, prioritize safety. “Stick to this zone where that’s what’s gonna be today,” was a key recommendation.

By following these guidelines, you can effectively manage fluctuating WBGT readings and keep your athletes safe during workouts.

When deciding between using Wet Bulb Globe Temperature (WBGT) or the “feels like” (heat index) measurement to guide practice decisions, the consensus is clear: WBGT generally allows for more flexibility in practice scheduling. 

Switching to WBGT can lead to more practice days, offering a more nuanced and accurate measure of heat stress than the heat index. While WBGT provides flexibility, it also ensures that practices are conducted safely, even during the hottest parts of the year. Here’s why:

Key Takeaways:

1. WBGT vs. Heat Index:
   • WBGT typically allows for more practice time compared to the heat index. Colin notes, “You’re gonna be able to practice a lot more with WBGT as opposed to heat index, just given the different variables that go into the two means of measurement.”
2. More Accurate Measurement:
   • WBGT considers multiple factors like wind speed, cloud cover, and humidity, leading to a more accurate assessment of heat stress. In contrast, heat index only measures temperature and humidity, often leading to higher “feels like” temperatures. As Colin pointed out, “If there’s a wind going or you’ve got a little bit of cloud cover, it’s gonna make your wet bulb a little bit lower.”
3. Real-World Example:
   • Colin shared an anecdote from Bryan, Texas, where a Chick-fil-A was concerned about transitioning to WBGT. On a random day, the heat index was above the threshold multiple times, but the WBGT remained within safe limits. “They had about five instances…where their heat index was above their threshold. But the wet bulb globe was below it, so they should have been absolutely fine.”
4. Experience from Schools:
   • Schools that have switched from heat index to WBGT have seen fewer practice delays. Josh Woodall from Bryan ISD noted, “The number of days that we had to modify or delay going outdoors because we had met the threshold with heat index was greater than the number of days that we would have to do that with the Wet Bulb Globe policy.”
5. Flexibility in Practice:
   • Using WBGT provides more opportunities to safely practice, even in hot conditions. Mike Hopper emphasized, “If we follow the heat index, we won’t see the field until September…whereas our wet bulb was sitting at probably like 84-85 where we’re not, you know, it’s not a big deal to us.”

Yes, Perry Weather provides the capability to pull detailed reports on daily weather conditions, including a breakdown of times spent in various heat levels like elevated WBGT. The platform logs data every 15 minutes from on-site weather stations, and this historical data can be easily accessed through the dashboard. 

You can export the data as a CSV file or take a screenshot for quick sharing. Explore these features yourself with a two-week free trial of Perry Weather.

A study led by Dr. Casa from the Korey Stringer Institute at the University of Connecticut revealed that Zelus’s results were inconsistent and often inaccurate. They habitually overestimated or underestimated WBGT values.  

While the Zelus app offers a convenient estimation, it lacks the reliability needed for precise heat stress management. According to recent studies conducted by Texas A&M, devices from Perry Weather and Kestrel significantly outperformed Zelus in terms of accuracy.

Perry Weather units generally offer more accurate readings over both the short and long term. Recent studies, including one at Texas A&M, showed Perry Weather devices in closer alignment with control units compared to Kestrel.

Kestrel readings can fluctuate significantly due to its lack of a solar radiation shield around its temperature and humidity sensor. This can lead to inconsistent results, especially as the sun’s angle changes throughout the day.

Pushing back the start time can be particularly effective if it reduces sun exposure, as Mike mentioned, “We started pushing back an hour… it makes a significant difference on the field.” Additionally, consider shortening game quarters and adding extra water breaks. 

If conditions reach the black WBGT level, it’s advisable to delay the start of the games. For red WBGT levels, rather than delaying the start, you should incorporate additional rest breaks during the game.

Look out for announcements about the Texas A&M study in the coming weeks. We will also provide our analysis and insights on this study to our customer base and webinar attendees.

Region 3 covers much of Texas, characterized by higher average temperatures and greater humidity. Athletes in Region 3 are more acclimated to higher heat and humidity due to consistently hotter climates, which justifies higher restrictions. 

Josh Woodall shares that athletes in drier, cooler areas like West Texas or the Panhandle in Region 2 are less acclimated to intense heat compared to those in humid regions. “It feels a lot different at five o’clock in the afternoon in Bryan compared to Midland”. Colin notes, “The hotter the average climate, the higher the category”. 

The UIL recommends to lower the WBGT threshold for younger athletes, like middle school or elementary athletes. Their bodies aren’t quite as matured and developed as an older high-school aged athlete, therefore they require some a more conservative approach.

The UIL does not differentiate between practice or games. As per the heat stress and athletic recommendations from the UIL, readings should be taken before and during every outside event or practice to accommodate accordingly based on adopted guidelines.

Studies have shown that “no difference in median WBGTs among three different athletic surfaces”.

To learn more about WBGT on different surface types, check out our blog “Comparing Wet Bulb Globe Temperatures Across Athletic Surfaces“.

Situations like this are up to individuals and their weather policies. Perry Weather is customizable to meet the standards of whatever you policy is. If you are looking to set your policiueis, here is the UIL recommendations. Perry Weather account executive will walk you through best practices and set your policies up for you.

It’s best to have an on-site station at each individual location as WBGT can vary significantly depending on immediate surroundings. Perry Weather stations are affordable and scalable and many of our clients have them on all campus locations in their district.

That said, some Perry Weather clients use data from stations located at nearby campuses, but proceed with caution as there are many variables that factor into calculating an accurate WBGT reading that may change based on location.

As of now, UIL’s stance on making WBGT zones mandatory instead of just recommendations remains uncertain. Perry Weather has been working closely with the UIL to provide extensive data, including supplying daily wet bulb readings to evaluate the impact on practices and games, to support their decision-making process. 

To avoid high afternoon temperatures, middle school football practices are typically scheduled in the morning. Josh notes that at Bryan ISD, “We’ve altered our schedules to where our middle school athletics are in the morning,” ensuring that practices are conducted before school hours. 

“Practicing in the morning means we have very few practices delayed or postponed because of weather conditions.” Morning practices reduce the risk of weather-related interruptions, such as thunderstorms that often occur in the afternoon. Practicing in the morning also helps condition athletes for the heat they will experience during games.

At Perry Weather, we can create groups whether it’s for certain coaches that are at certain fields, if they’re off campus, if you’ve got some on campus, so only certain groups are receiving policy warnings relative to their activity guidelines. You can isolate those messages within the Perry weather application to a specific group that go out in real time. 

Policies from organizations like UIL (University Interscholastic League) generally do not specify a minimum duration for which the heat level must stay in a certain zone before taking action. Colin points out that as soon a heat level threshold is reached, an alert should be issued to coaches. “Since there’s no indication on how long it needs to be, we send the alert immediately at that point”.