9. Athletes' threshold UC Davis coaches plan practice times around the heat. On the East Coast, where humidity brews, an 80/80 test is used to determine if outdoor practices are safe: If the temperature is 80 degrees with 80 percent humidity or above, athletes aren't safe, says UC Davis athletic trainer Lisa Varnum. With little humidity here, she said the school relies on the air quality index, which ranks air from good to hazardous. Some team practices will continue when air is deemed unhealthy for sensitive groups, but athletes with asthma and other problems can sit out. Once air reaches the generally unhealthy mark, outdoor practices are called off or moved to cooler times of the day, like early morning.