A heat wave is a prolonged period of abnormally high temperatures, usually lasting two or more days, often accompanied by hot winds and dry conditions, and high humidity. In many regions, a heat wave is declared when temperatures exceed 35°C to 40°C, depending on local norms. In India, the India Meteorological Department (IMD) declares a heat wave when temperatures reach:
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≥ 40°C in plains
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≥ 37°C in coastal areas
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≥ 30°C in hilly regions
Or when the temperature rises 5°C to 6°C above normal for that location.
To understand the danger, consider that the normal human body temperature is around 37°C (98.6°F). When the outside temperature equals or surpasses this, your body struggles to cool itself, especially if humidity is high and sweat can’t evaporate easily.
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Contents
How Heat Affects the Body
The body cools itself mainly by sweating and increasing blood flow to the skin. However, these systems may become overwhelmed during a heat wave, especially in humid conditions.
1. Brain and Nervous System
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Effect: Heat can interfere with the brain’s ability to regulate temperature.
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Symptoms: Confusion, headache, dizziness, fainting, or unconsciousness.
2. Skin and Circulatory System
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Effect: More blood is sent to the skin to release heat, which can reduce blood flow to vital organs.
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Symptoms: Red, hot skin; rapid heartbeat; low blood pressure; excessive sweating (early stage) or dry skin (late stage).
3. Kidneys and Dehydration
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Effect: Sweating leads to fluid and salt loss, straining the kidneys.
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Symptoms: Fatigue, dark urine, muscle cramps, and dry mouth.
4. Muscles
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Effect: Loss of sodium and potassium through sweat can lead to cramps and weakness.
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Symptoms: Painful muscle cramps, especially during or after physical activity.
What to Do: Immediate Care and Prevention
First Aid for Heatstroke/Sunstroke:
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Move to a cool place: Shade or an air-conditioned space.
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Cool the body:
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Remove excess clothing.
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Apply wet cloths or pour normal temperature water over the body.
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Fan the person or use a cool shower.
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Rehydrate: If conscious, give ORS, lemon water, torani (rice water), or any hydrating drink.
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Seek medical help immediately: Heat stroke can be fatal without urgent care.
How to Prevent Heat Illness During a Heat Wave
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Stay hydrated – drink water regularly.
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Avoid going out during peak heat (11 a.m. to 4 p.m.).
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Wear light, breathable clothes.
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Use fans, cool baths, and stay in shaded or air-conditioned areas.
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Check on vulnerable people – the elderly, children, and those with medical conditions.
Why Are Heat Waves Dangerous?
Health Risks
Prolonged exposure to extreme heat can lead to dehydration, heat exhaustion, and heat stroke. Heat stroke is a medical emergency that can be fatal if not treated promptly. It causes confusion, high body temperature, and unconsciousness.
Increased Illness and Death
Older adults, children, people with chronic illnesses, and outdoor workers are especially vulnerable. Each year, thousands of heat-related deaths occur globally, and most are preventable.
Infrastructure Strain
During heat waves, the demand for electricity spikes due to widespread use of air conditioning. This can lead to power outages. Roads, railways, and even water systems may also suffer damage.
Environmental Impact
Heat waves often dry out landscapes, increasing the risk of wildfires and harming agriculture and water supplies.
Who’s Most at Risk?
Several Indian states experience severe and deadly heat waves, especially between April and June.
| State | Typical Max Temp (°C) | Recent Heat Wave Peaks |
|---|---|---|
| Rajasthan | 45°C – 49°C | Phalodi recorded 51°C (India’s highest, 2016) |
| Uttar Pradesh | 43°C – 46°C | Banda, Jhansi often cross 47°C |
| Bihar | 42°C – 45°C | Heat waves are linked to dozens of deaths yearly |
| Odisha | 40°C – 44°C | Frequent severe heat warnings are issued |
| Telangana & Andhra Pradesh | 42°C – 46°C | The 2015 heat wave killed over 2,000 people |
| Delhi-NCR | 44°C – 48°C | Regular heat wave warnings are issued |
| Gujarat | 42°C – 45°C | Combined with dry winds, the risk is high |
These states are especially vulnerable due to dense populations, poor access to cooling, and exposure of outdoor workers.
Final Thought: Climate Change and the Future
Heat waves in India are becoming more frequent, intense, and widespread due to climate change. States like Rajasthan, Telangana, and Uttar Pradesh are already on the frontlines. Community awareness, better infrastructure, and preparedness at both personal and policy levels are critical to saving lives.
By staying alert and taking action, we can protect ourselves and our loved ones from the dangers of extreme heat. A little preparation can go a long way when the temperature soars.
Remember: The most important goal is to reduce the body temperature and prevent further dehydration. Prompt action can save a life.
Sources: Ready.Gov, WHO, National Disaster Management Authority (NDMA).
