Heat Index vs WBGT: Why Traditional Temperature Readings Are Not Enough

Why It Matters


Every year, student-athletes suffer heat-related illnesses — some even fatal.
 Traditional temperature readings (like the heat index) don’t tell the full story.
To protect athletes, we must measure true environmental stress on the body.


What Is the Heat Index?


Heat Index = Temperature + Humidity

  • Often used in weather reports
  • “Feels like” temperature
  • Assumes shady, light wind conditions


Not reliable for sports safety decisions because it does NOT include direct sun, wind, or ground heat
Often underestimates actual risk during athletic activity!


What Is WBGT? (Wet Bulb Globe Temperature)


A scientific measure of environmental stress on the body that combines:

  • ☀️ Solar radiation
  • 💧 Humidity
  • 🌡️ Air temperature
  • 🌬️ Wind speed


WBGT is measured using a specialized device with 3 sensors:

  1. Wet bulb (humidity + evaporative cooling)
  2. Dry bulb (air temp)
  3. Black globe (radiant heat from sun)

WBGT is the gold standard for preventing exertional heat illness in athletes

Why Heat Index Falls Short–The Factors:


Heat Index

  • Air Temperature – ✅
  • Humidity – ✅
  • Solar Radiation ☀️ – ❌
  • Wind Speed 🌬️ – ❌
  • Surface Heat 🔥 – ❌

WBGT

  • Air Temperature – ✅
  • Humidity – ✅
  • Solar Radiation ☀️ – ✅
  • Wind Speed 🌬️ – ✅
  • Surface Heat 🔥 – ✅


Heat Index doesn’t account for turf heat or direct sun exposure and is used to determine general public safety, not athletic activity safety.
Otherwise, you underestimate risk, especially for outdoor sports.

Recommendations for Athletic Programs


Use WBGT to guide practice intensity, uniform modifications, and rest/water breaks

Establish a Heat Policy using WBGT thresholds:


⚠️ <82°F WBGT: Normal activity with standard precautions


⚠️ 82–86.9°F: Monitor at-risk athletes, scheduled breaks


⚠️ 87–89.9°F: Shortened practice, equipment removed


⚠️ 90–92°F: Limited practice time, helmets only


⚠️ >92°F: No outdoor activity