With increasing concerns about heat-related hazards for athletes, many commercial weather companies are offering heat monitoring systems. Such systems may provide readily available data across a school campus that can free busy staff such as coaches and athletic trainers from data collection. Yet, standard recommendations are for measurements to be taken on the field of play. A question is “can a single weather station accurately capture heat stress conditions on different fields of play with differing microclimates?” Our study compares wet bulb globe temperature (WBGT) reports from a WeatherSTEM operated weather station to those collected during a summer study period on nearby fields of play (grass, synthetic turf, and hardcourt tennis) on the campus of the University of Georgia, Athens, GA, USA. The WeatherSTEM WBGTs were lower than on-site measurements 84%–92% of the time, resulting in clinically meaningful differences in activity modification recommendations. We believe these differences are related to both meteorological conditions from the station siting on a roof and the WBGT model employed. Among other factors, we believe that the greater wind speeds at the weather station reduced estimated WBGTs. Also, simply replacing the WeatherSTEM WBGT model with a publicly available, physically based model increased WBGT estimates and better matched on field conditions. We conclude that station setting and the choice of software for computing WBGT can make a critical difference in determination of the WBGT estimates and associated activity modification recommendations. Users should also request information on the validity and accuracy of WBGT estimates prior to purchasing a system.