Hot weather can affect anyone, but some people run a far greater risk of serious harm. Understanding what actually happens inside the body makes the standard advice make sense, and makes the warning signs recognisable.
The chain of events
As the body gets hotter, blood vessels open up. That is how the body sheds heat — moving warm blood towards the skin. The cost is that it lowers your blood pressure, and the heart has to work harder to push blood around.
That alone can produce mild effects: an itchy heat rash, swollen feet and ankles, light-headedness on standing.
At the same time you sweat, and sweating loses both fluid and salt. Crucially — and this is the part usually left out — it is the balance between them that changes. That is why drinking large volumes of plain water in extreme heat is not automatically the right answer: it replaces the fluid while diluting the salt further.
Who is most at risk
Experts recommend extra precautions for those more vulnerable: older people, babies and young children. Older people sweat less efficiently and feel thirst less reliably. Small children have a high surface area relative to their size and depend entirely on an adult noticing.
Add to that anyone working outdoors, anyone on medication that affects fluid balance, and anyone with heart or kidney disease.
What it means in Bangladesh
This is not a foreign-weather story here. Bangladesh has had heatwaves severe enough to close schools nationwide, and the combination that makes Bangladeshi heat dangerous is not temperature alone but temperature plus humidity. Sweat cools you by evaporating; in very humid air it evaporates poorly, so the body's main cooling mechanism works at a fraction of its capacity. A 36°C day in Dhaka is physiologically harder than a 40°C day in a dry climate.
Three practical points follow, and the salt one is the most neglected. For anyone sweating heavily for hours — a rickshaw puller, a construction worker, a farmer, a garment worker in an unventilated floor — plain water alone is not enough. Oral saline is cheap, available in every pharmacy in the country, and is the correct answer; so is lemon, salt and sugar in water, or plain rice starch with a pinch of salt.
Know the order of the warning signs, because heat exhaustion is treatable and heatstroke is an emergency. Exhaustion looks like heavy sweating, cramps, headache, nausea, dizziness and pale clammy skin — move the person somewhere cool, lie them down, raise their feet, give them fluid with salt in it. The line to watch for is a change in behaviour: confusion, slurred speech, or a person who has stopped sweating and whose skin is hot and dry. That is heatstroke, and it needs a hospital immediately, cooling them on the way.
Finally, the person most at risk in a Bangladeshi household is usually the one nobody is watching — an elderly relative resting alone in a closed upstairs room during a load-shedding afternoon. Heat kills quietly and indoors more often than it does dramatically outdoors.
