Heatstroke, also known as sunstroke, is a life-threatening condition that occurs when the body temperature exceeds 104 degrees F (40 C). This most extreme form of hyperthermia or heat-related illness is typically due to extended exposure to high temperatures or physical activity in hot and humid environments.

Heatstroke can lead to serious consequences such as brain damage, organ failure, or fatality by causing the body to overheat. The condition may manifest with symptoms such as confusion, seizures, or loss of consciousness. It is during summertime that this condition is the most frequent.


Heatstroke is a critical medical condition. Its signs and symptoms may include:

  • Elevated body temperature: The primary indicator of heatstroke is a core body temperature reaching 104 F (40 C) or higher, measured with a rectal thermometer. This may include hot, flushed skin or notably pale skin.
  • Anhidrosis: Or absence of sweating, especially prevalent in non-exertional heatstroke.
  • Unusual and persistent sweating even after discontinuing physical activity, which is more frequent in exertional heatstroke.
  • Ataxia: Heatstroke can lead to difficulties with movement and coordination.
  • Altered mental state or behavior: Heatstroke may lead to confusion, agitation, slurred speech, irritability, delirium, seizures, and even coma.
  • Nausea and vomiting: Individuals experiencing heatstroke may exhibit vomiting or feel nauseous.
  • Audible lung crackles: Such as bubbling or gurgling sounds in the lungs.
  • Rapid breathing: Heatstroke can cause breathing to become quick and shallow.
  • Tachycardia: Or accelerated heart rate as the heart works intensely to aid in cooling the body under heat stress.
  • Headache: Heatstroke may lead to a throbbing sensation in the head.
  • Oliguria, or low urine output
  • Seizures
  • Syncope (fainting) or loss of consciousness.
  • General weakness.

If heatstroke is suspected, urgently seek medical help, and make efforts to quickly reduce the individual’s body temperature.

Immediate steps to cool the individual may include moving them into the shade or indoors, removing excess clothing, and employing various means to cool them down, such as placing them in a cool tub of water, using a cool shower, or applying ice packs or cold, wet towels to their head, neck, armpits, and groin.


Heatstroke occurs when the body’s natural cooling mechanisms fail to adequately regulate its temperature. Typically, the hypothalamus, a crucial part of the brain responsible for regulating bodily functions, maintains the core body temperature at approximately 98.6°F (37°C). However, if the body absorbs more heat than it can dissipate, the internal temperature surpasses this normal level, resulting in heatstroke.

Heatstroke can occur in two main ways:

  • Hot environment exposure: This type is more common in older adults and those with chronic illnesses. In nonexertional or classic heatstroke, being in a hot environment, especially in hot and humid weather for a long time, causes a rise in body temperature.
  • Strenuous activity: This type is more likely to happen to people who are not accustomed to hot weather or conditions. Exertional heatstroke results from intense physical activity in hot weather, affecting anyone exercising or working in high temperatures.

In both types of heatstroke, the condition can be triggered by factors such as wearing excessive clothing, consuming alcohol that affects the body’s temperature regulation and becoming dehydrated due to insufficient water intake.

Risk factors

Heatstroke can occur to any person at any age. However, certain factors make a person more susceptible to heatstroke, such as:

  • Age: Infants and the elderly faces a higher risk due to potential difficulties in regulating body temperature. The inability of both age groups to stay hydrated typically raises risk. The central nervous system is not fully developed in babies and toddlers, and it starts to degrade in individuals over the age of 65.
  • Sudden exposure to hot weather: People who experience an abrupt rise in temperature, such as a trip to a hotter region or that of an early summer heat wave, may be more vulnerable to heat-related illnesses.
  • Exertion in hot environments: Individuals engaged in physically demanding activities in hot environments, like athletes, soldiers, or those with strenuous occupations, are more susceptible to heatstroke. Reduce physical activity for a few days to let the body adjust to the new conditions. However, be aware that the risk of heatstroke may remain elevated until one been exposed to higher temperatures for several weeks.
  • Inadequate air conditioning: Air conditioning is the best way to cool down and reduce humidity when it is extremely hot outdoors.
  • Certain drugs: Stimulants used for attention-deficit/hyperactivity disorder (ADHD) and illegal stimulants like amphetamines and cocaine can increase susceptibility to heatstroke. Generally, the use of medications like diuretics, sedatives, vasoconstrictors, tranquilizers, beta blockers, antidepressants or antipsychotics, or heart and blood pressure medications that impact temperature regulation elevates one’s risk.
  • Certain diseases: Conditions that may affect sweat production include cystic fibrosis, and various medical conditions related to the heart, lungs, kidneys, liver, thyroid, or blood vessels can elevate the risk. Risk also increases among people having a high fever, obesity, or a heatstroke history.