Heatwave vs heatstroke: What's the difference?

As temperatures soar across several parts of India, emergency rooms are reporting a constant rise in patients complaining of dizziness, weakness, dehydration, vomiting and sudden collapse after prolonged exposure to heat.

But amid the worsening summer conditions, doctors say many people continue to misunderstand one crucial distinction - the difference between a heatwave and heatstroke.

To understand this better, Firstpost spoke with Dr Mohit Sharma, Senior Consultant, Internal Medicine, Amrita Hospital, Faridabad.

“A heatwave and heatstroke are not the same thing”

“The health risk is growing, but many people still confuse ‘heatwave’ and ‘heatstroke’ as the same thing, although they are very different medical conditions,” said Dr Sharma.

“As India faces longer and more intense summers, it is becoming more important to understand the difference,” he added.

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According to him, a heatwave is an environmental condition, while heatstroke is a medical emergency that happens when the body can no longer cool itself effectively.

“A heatwave is one type of environmental condition,” he explained. “Exposure to heat can lead to heat stroke in humans. One of them is the weather. The second is the body’s failure to cool down.”

What exactly is a heatwave?

A heatwave is officially declared when temperatures remain significantly above a region’s normal average for several consecutive days.

Factors such as extreme heat, humidity, dehydration, crowded environments and prolonged physical exertion can increase the risk of heat-related illness during such periods.

Doctors say the body normally attempts to regulate temperature through sweating and increased blood circulation to the skin.

“The body often fights the situation by changes in circulation and perspiration,” Dr Sharma mentioned. “Evaporation cools the body through sweat. Blood flow is also increasing to the skin to release heat.”

Why heatstroke is considered a medical emergency

Heatstroke, however, occurs when this cooling system begins to fail.

It is a potentially life-threatening condition in which the body’s internal temperature rises rapidly - often above 104°F. If untreated, it can damage major organs including the brain, kidneys, heart and muscles.

“The danger is that heat illness often starts quietly,” shared Dr Sharma. “They just think they’re tired and don’t see the early signs.”

The warning signs many people ignore

According to Dr Sharma, the body often sends multiple warning signals before heatstroke develops fully.

Some of the early symptoms of a heatstroke include profuse sweating, headaches, muscle cramps, nausea, unusual fatigue, dizziness, agitation, and dark urine.

However, many people continue with daily activities despite experiencing these symptoms.

“But these symptoms don’t usually stop people from travelling, working or exercising,” Dr Sharma warned.

Why hotter nights are becoming dangerous

Doctors are particularly concerned about rising night-time temperatures, which reduce the body’s ability to recover from daytime heat exposure.

“The body generally recovers during cooler nights,” stated Dr Sharma. “But the tension is mounting as the evenings remain warmer.”

“That’s when people just drop dead, after what seemed like a normal day,” he added.

Doctors urge people to treat heatwaves as a serious health risk

Medical experts now say that preventing heat-related illness should be treated as a major public health priority during extreme summer conditions.

Doctors recommend avoiding direct sunlight whenever possible, especially between 12 pm and 4 pm.

Even if a person does not feel thirsty, regular hydration remains essential. ORS solutions, electrolyte-rich drinks and coconut water can help maintain hydration levels during outdoor activity and prolonged heat exposure.

Experts also advise eating light meals, wearing loose cotton clothing, ensuring proper indoor ventilation, and avoiding strenuous outdoor activity during peak heat hours.

The hidden danger of parked cars

Doctors have also warned against leaving elderly individuals or children inside parked vehicles, even briefly.

Closed vehicles can heat up rapidly and become dangerously hot within minutes, significantly increasing the risk of heatstroke.

“The body gives warnings before shutting down”

Dr Sharma stressed that heatstroke does not always appear dramatically or suddenly.

“Heatstroke does not always happen in a dramatic way,” he said. “The body sends out many warnings before shutting down.”

“That’s the problem - most people find out too late about them.”