Heat illness may be viewed as a range of ailments related to the body’s inability to cope with heat. It includes minor problems such as heat rash (prickly heat), heat cramps, and heat exhaustion. Heat stroke is the most severe form and is defined as a body temperature higher than 41.1°C (106°F) associated with neurological (brain) dysfunction. Exertional heat stroke (EHS) generally occurs in young individuals who engage in strenuous physical activity for a prolonged period of time in a hot and sometimes even in a not-so-hot environment. It can start as heat cramps that can be completely disabling and typically occur during or after hard work and are caused by electrolyte deficiencies that result from extended periods of intense sweating. Symptoms include painful spasms of leg, arm or abdominal muscles, heavy sweating and thirst. Drinking plenty of water or electrolyte fluids are the suitable first aid. EHS happens when the individual’s capacity to dissipate or drive away the heat produced by overactive muscles falls short. The temperature rises to such high that the body becomes a pressure cooker and starts (am tempted to say) cooking our internal organs, inflicting severe tissue damage resulting into multi-organ failure. We frequently read news about young men (and women) collapsing and dying with no apparent reason when made to undergo severe physical excretion for endurance tests during recruitment in the Indian police force or military. High (body) core temperatures damage the internal organs, especially the brain. The main reason is the fluid loss in the form of sweat, sometimes even ‘one and half’ liter in one hour and three liters in two hours. Along with sweat we also lose electrolytes. Enormous fluid loss can also lead to dangerously low blood volume and lead to dangerously low blood pressure. This can break down the body’s cooling system that demands increased blood flow to the skin to take away the heat from body’s core. Electrolyte imbalance adds insult to injury, causing irregularities in heart function. Most people who are killed by heat stroke die when their heart stops pumping effectively (mostly the cause of death is written as ‘heart failure, or cardiac arrest and that is why heatstroke death numbers seem so low). Even people who survive are likely to have permanent brain damage if their core temperature has been over 40.6°C (105°F) for more than an hour or two. The risk factors for EHS in such young men and women depend on the number of active sweat-glands, acclimatization, outside temperature, humidity, hydration status and activity-related factors (duration of exercise). Acclimatization means gradual introduction of a sportsperson or a worker to the ‘outdoor’ task. For instance, the new recruit can start his/her exercise/work only in the morning or for gradually increasing time periods during the first few days. Such acclimatization on the playground or outdoor places like construction sites, or mines, should take place under close supervision by experienced trainers/safety managers; the new sportsperson/worker should have standing permission to withdraw to cooler conditions any time symptoms of intolerance occur. People with diabetes, high bold pressure or any other chronic illnesses must be kept under watch. During heat waves even acclimatized people may warrant a change in timings. Overweight people are at a greater risk because every movement requires greater muscular effort and therefore generates more heat than in a normal weight people. In addition, obesity often means an inactive lifestyle with resulting lower aerobic capacity and total absence of heat acclimatization.