According to the National Center for Catastrophic Sports Injury Research (NCCSIR), when football activity is carried on in hot weather, the following ten suggestions and precautions should be taken:
1. Require pre-participation physicals. Each athlete should have a complete physical examination (PPE) , including questions about any history of previous heat illness, and sickle cell trait , before practice begins.
2. Make sure athletes are acclimatized to the heat. Athletes need to become adjusted to exercising in the heat and humidity of pre-season football practices by following the NATA's pre-season heat acclimatization guidelines .
3. Monitor environmental conditions: The NCCSIR recommends use of a sling psychometer to measure relative humidity, and that any time the wet-bulb temperature is over 82 degrees Fahrenheit (28 degrees Celsius), careful control of all activity should be undertaken. It notes that the American College of Sports Medicine, NATA, NFHS, and the NCAA all have published guidelines for conducting athletic activities in hot and humid environments. For a set of guidelines from the Tennessee Secondary School Athletic Association based on the heat index,  click here .
4. Adjust activity levels in hot weather. The intensity of exercise, says the NCCSIR, is the leading factor that can increase core body temperature higher and faster than any other. Adjusting activity level and providing frequent rest periods in cool, shaded areas with some air movement and helmets removed and jerseys loosened or removed can minimize the risk of heat illness in football. Multiple practice sessions during the same day should be minimized (note: under the current heat acclimatization guidelines , two-a-days are prohibited during the first five days, although it should be noting that an Executive Summary  issued by NATA in June 2014 about revised guidelines, which were originally supposed to be issued later that summer but are not now expected to be issued until August/September 2015, permit two-a-days, as long as they are not any longer than an hour in duration).
5. Drink on a schedule. Fluids should be readily available and players should be encouraged to drink frequently throughout a practice session. Athletes should drink water before, during, and after practice . Sports drinks containing sodium (salt) and potassium can be consumed to replace electrolytes lost during exercise . [Although the NCCSIR doesn't talk about energy drinks , it is important for athletes to understand that they are NOT intended to use for hydration]
6. Monitor athletes' weight: Athletes should be weighed each day before and after practice and weight charts checked in order to treat the athlete who loses excessive weight each day (e.g. those who perspire heavily). Generally, athletes should return to their previous day's weight before the next day's practice.
7. Wear moisture wicking clothing. Clothing is important and a player should wear moisture wicking apparel to dissipate heat; never use rubberized clothing or sweatsuits.
8. Identify at-risk athletes. Some athletes are more susceptible to heat injury, including those not accustomed to physical activity in the heat, those who are overweight, ill with a fever, or other medical condition (such as sickle cell trait )(for an article risking risk factors for heat illness, click here ), or who constantly compete at their maximum capacity and ignore warning signs  of heat illness. Athletes with previous heat problems should be monitored.
9. Have an emergency action plan. Sports teams should have an Emergency Action Plan (EAP)  in place, all personnel should have copies, and procedures should be reviewed and practiced annually.
10. Know signs and symptoms of heat illness and how to treat them: Coaches, athletes, and athletic trainers should know the signs and symptoms of heat illness , and follow best practices when it comes to preventing and treating heat illness (cool first, transport second) , including being prepared by having plastic outdoor tubs or swim pools filled with ice water at practice facilities in hot and humid conditions.
Source: Kucera KL, Klossner D, Colgate R, Cantu RC. Annual Survey of Football Injury Research 1931-2014. National Center for Catastrophic Sports Injury (March 2015)