Heat stroke: A hidden killer in extreme temperatures

When temperatures soar beyond comfort, the human body fights hard to stay cool but sometimes, it loses the battle. Heat stroke is not just about feeling overheated it’s a rapid, life-threatening condition that can shut down vital organs within minutes.

As global temperatures rise and heat waves become more intense, understanding heat stroke is no longer optional it’s essential for survival.
A heat wave is a period where local excess heat accumulates over a sequence of unusually hot days and nights.

Heat waves and prolonged excess heat conditions are increasing in frequency, duration, intensity and magnitude due to climate change.
Even low and moderate intensity heat waves can impact the health and well-being of vulnerable populations.

The frequency and intensity of extreme heat and heat waves will continue to rise in the 21st century because of climate change.

Extended periods of high day and nighttime temperature conditions create cumulative stress on the human body, increasing the risk of illness and death from heat exposure.

Heat waves can acutely impact large populations for short periods of time, often trigger public health emergencies, and result in excess mortality and cascading socioeconomic impacts (for example, lost work capacity and labor productivity).

They can also cause loss of health service delivery capacity, when power shortages accompany heat waves and disrupt health facilities, transport and water infrastructure.

An intense, early-season heat wave has gripped Pakistan as of late April 2026, with severe, potentially fatal conditions impacting Sindh, southern Punjab, and Baluchistan.

Temperatures in these regions have surged to 45-50°C (113-122°F), while high humidity in cities like Karachi has made it feel even hotter, leading to a surge in heatstroke cases, particularly among outdoor workers.

The National Disaster Management Authority (NDMA) issued warnings for an intense heat wave persisting until May 5, 2026, with continued threats through May and June.

The NDMA said the current weather pattern was consistent with its seasonal outlook issued three to four months earlier, and noted that a detailed assessment for the April to June period had already been shared.

According to the advisory, Sindh, southern Punjab and parts of Baluchistan were expected to face severe heat wave conditions.

Major cities including Karachi, Hyderabad, Sukkur, Larkana, Jacobabad, Bahawalpur, Rahim Yar Khan, Multan and Turbat were likely to remain under extreme heat.

The amount of heat stored in the human body is determined by a combination of an inability to eliminate internally generated heat from metabolic processes due to environmental heat stress (for example, high temperature, high humidity, low wind, high thermal radiation), clothing creating a barrier to heat loss, external heat gain from the environment.

Heat can also disrupt and compromise essential health services, such as the loss of power supply and transport.

Heat will reduce working productivity and increases the risk of accidents. It is difficult to complete work or learning in very hot weather and heat waves may lead schools and other institutions to close. Heat waves can also be associated with hazardous air pollution events.

The scale and nature of the health impacts of heat depend on the timing, intensity and duration of a heat event, and the level of acclimatization and adaptability of the local population, infrastructure and institutions to the prevailing climate.

What actions should the public take?

• Avoid going outside and doing strenuous activity during the hottest time of day.
• Stay in the shade. Remember that perceived temperatures in the sun can be 10–15˚C higher.
• Spend 2–3 hours during the day in a cool place.
• Stay informed about official heat warnings.

Keep your body cool and hydrated:

• Use light and loose-fitting clothing and bed linens.
• Take cool showers or baths.
• Wet your skin using a damp cloth, spray, or wet light clothing.
• Drink water regularly (1 cup of water per hour and at least 2–3 liters per day).
• Regularly check in with vulnerable people in your circle especially people over 65 years old and those with heart, lung or kidney conditions, a disability, and living alone.

Mitigating climate change by reducing greenhouse gas emissions is imperative and urgent to limit the magnitude of human costs from extreme heat.

WHO is addressing climate change through the Alliance for Transformational Change in Climate and Health (ATACH) as well as country support of technical and policy resources to help the health sector and communities adapt to the risks of climate change.

The sun doesn’t warn before it strikes but you can prepare before it does. Heat stroke isn’t just a summer inconvenience.

It’s a silent killer that moves fast and leaves little room for error. Stay alert, stay hydrated, and remember one smart decision today could save a life tomorrow.