A University of Georgia study has found that a popular smartphone app used to gauge heat risk underestimates dangerous temperatures and the need for activity modifications during hot weather. The app often reported temperatures up to 4 degrees cooler than on-site wet bulb globe temperature measurements, which factor in heat, humidity, wind, and sun exposure.
Researchers collected data over two months from 26 high schools across 11 states. They found the app was especially unreliable at WBGTs above 90°F, when timely decisions—like shortening practice or increasing water breaks—are critical.
“Heat is the leading weather-related killer in the U.S.,” said lead author Andrew Grundstein. “It’s vital that monitoring tools are accurate.”
Despite growing interest in mobile heat safety tools, the study concludes that onsite WBGT measurements remain the most reliable method for protecting athletes, students, and outdoor workers from heat-related illness. The findings were published in Geo Health on March 25.
