Effects of Extreme Heat on the Human Body
- Sylvia Rose
- Mar 22
- 4 min read
Extreme heat is a pressing reality for many parts of the world. Hazardous temperatures bring exhaustion, breathing problems, heatstroke, organ collapse and death.
The body is designed to operate in a narrow temperature range, around 98.6°F (37°C). Thermoregulation maintains equilibrium to keep the body at optimal function.
Sweating
Exposed to high temperatures the human body rapidly sheds excess heat, through sweat. When natural mechanisms get overwhelmed the body sicken. Humidity is major factor in the impact of heat.
As sweat evaporates from the skin, it draws heat away from the body. In humid conditions, evaporation is less effective. Humidity can make temperatures feel hotter. Everything seems heavy, damp and sticky.
High humidity hinders evaporation, so sweating is less effective. When fluid is lost, dehydration is a concern. Even mild dehydration (2-3% loss of body weight) can impair brain function and increase accident risks.
Vasodilation
At the same time, blood vessels dilate. This allows more blood to flow closer to the skin's surface, where heat can be radiated away.
Increased blood flow strains the cardiovascular system. It forces the heart to work harder to circulate blood.
Heat Exhaustion & Heat Stroke
Heat Exhaustion
If the body can't shed heat fast enough, it enters a state of heat exhaustion. It happens when the body loses too much water and salt by sweating.
Symptoms of heat exhaustion include
Heavy sweating: In the body's efforts to cool down, sweating can increase.
Weakness and fatigue: The body's resources are drained as it struggles to regulate temperature.
Dizziness and nausea caused by reduced blood flow to the brain.
Headache: Due to dehydration and electrolyte imbalances.
Muscle cramps: Loss of electrolytes through sweat can cause painful muscle spasms.
Heat exhaustion is a warning sign. If left untreated, it can progress to heat stroke, a life-threatening medical emergency.
Heat Stroke
Heat stroke occurs when the body's thermoregulatory system completely fails. Body temperature rises rapidly, often exceeding 104°F (40°C). The intense heat can damage vital organs, including brain, heart, and kidneys.
Symptoms of heat stroke include
High body temperature: Core body temperature is elevated.
Confusion, disorientation, and slurred speech: Brain function is severely impaired.
Seizures: The nervous system is overwhelmed.
Hot, dry skin or profuse sweating: Sweating may stop entirely, or the body continues to sweat profusely depending on type of heat stroke.
Loss of consciousness: The body shuts down.
Heat stroke needs immediate medical attention. It can lead to permanent disability, organ damage and death.
Extreme Heat: Prolonged Exposure
Prolonged exposure to extreme heat can have long-lasting detrimental effects on the body.
Cardiovascular Strain: The constant effort to circulate blood during vasodilation can strain the heart and increase the risk of heart attacks and strokes, especially in individuals with pre-existing cardiovascular conditions.
Kidney Damage: Dehydration and reduced blood flow to the kidneys can lead to kidney damage and increase the risk of kidney stones and chronic kidney disease.
Respiratory Problems: Hot, stagnant air can worsen respiratory conditions like asthma and COPD. This is exacerbated by air pollution, which also raises heat levels.
Electrolyte Imbalance: Excess sweating causes loss of vital electrolytes like sodium, potassium, and magnesium, which are important to nerve and muscle function.
Chronic dehydration contributes to kidney dysfunction. An elevated heart rate from heat stress can cause heart attack or long-term cardiovascular problems.
Consistent exposure to extreme heat brings mental health issues, like depression and anxiety. According to the World Health Organization (WHO) heat-related health problems can triple in the coming decades. Currently up to 500,000 heat-related deaths happen a year.
Nepal experiences extreme heat and heatwaves, especially during the summer months (May to July), with temperatures sometimes reaching 44°C (111°F).
Vulnerable People
While anyone can be stricken by extreme heat, certain populations are more vulnerable.
Elderly: Bodies are less efficient at regulating temperature.
Infants and young children: Bodies are still developing and have a harder time adapting to extreme temperatures.
People with chronic illnesses: Conditions like heart disease, diabetes, and respiratory problems increase vulnerability.
Outdoor workers: Exposed to the heat for extended periods.
People without access to air conditioning: Lack of access to cooling make it hard to escape the heat.
Urban residents with limited access to shaded or cool spaces.
Athletes: Intense physical activity in hot weather can quickly cause overheating.
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