For interscholastic athletes participating in outdoor sports, excessive heat can affect health, safety, and performance. Increasingly, many state high school associations have mandated weather-based activity modification and acclimatization policies, among other factors, to reduce exertional heat illnesses (EHIs) risk. Yet, modulating the practice schedule towards cooler times of the day, has not been widely used in interscholastic sports, in part because disruptions of predicable schedules can be difficult for athletic staff, athletes, and parents. We identified time-activity patterns of American football players in Georgia, U.S., to identify the variations in heat hazards and identify patterns that can be used for planning. Our dataset includes information on the date and time of practice, the activity type (game, scrimmage, practice), the wet bulb globe temperature (WBGT) and the occurrence of EHIs (i.e. heat exhaustion and heat syncope). We observed that practices tend to be held in the afternoon following the school day, while games/scrimmages mostly occur during the cooler evenings. These hotter afternoon conditions help explain the greater heat exhaustion / heat syncope illness rates observed for practices than for games or scrimmages. Our results show that shifting practices to the evening during the first four weeks of the season would reduce the likelihood of sessions exceeding 27.78oC WBGT by 32-55%. Adjusting practice schedules during the hottest weeks of the season is a way to reduce exposure to heat hazards and provide a predictable schedule for athletic staff, athletes and parents to follow.