Regardless of one’s level of athletic activity, training and/or competing outdoors in hot conditions (air temperature >30–35°C) poses significant challenges in terms of thermoregulation, hydration, and ultimately athletic performance. In extreme cases, these conditions can have dramatic consequences if the intensity and/or duration of exercise is maintained. As climate change leads to increased exposure to heat, it becomes essential to provide information and recommendations that will help minimize the risks faced by athletes of all levels. When possible, repeated exposure to heat stress (for example, 60 to 90 minutes at 35–40°C and 40% relative humidity) over 7 to 14 days allows the body to acclimate to the heat. Hydration also plays a vital role in compensating for fluid losses (sweat, the amount of which increases in hot environments), which help dissipate the excess heat produced by the muscles. Similarly, the selection and use of cooling strategies (e.g., external application [immersion in cold water], internal [cold drinks or crushed ice], or a combination thereof, administered before, during, or after exercise in hot conditions) lead to improved physiological and psycho-cognitive tolerance and enhanced athletic performance. Regardless of these measures, a number of recommendations should be adopted by athletes and all other participants—whether active or passive—in training or sports competition (officials, coaches, staff/volunteers, and spectators), while also planning for the restriction, postponement, or cancellation of outdoor physical and sports activities.