5.10 — Extreme Heat and Extreme Cold

These kill more people than the dramatic hazards in this Part and receive a small fraction of the attention, because they arrive slowly and without spectacle.

And almost all of the deaths are preventable by a small number of unglamorous actions.

Extreme heat

Who is at risk

Not the people you would guess.

Older people living alone, particularly those on medication that affects temperature regulation or fluid balance, and particularly those who do not perceive heat or thirst well.

Infants and small children.

People with chronic illness — heart, lung, kidney, diabetes.

People working outdoors, and this is the largest group in India: construction, agriculture, delivery, street vending.

People in poorly ventilated housing, particularly upper floors and metal roofs.

And anybody exercising in the heat, who is frequently young and fit — exertional heat illness affects the healthy.

The medical side

3.6 covers heat exhaustion and heat stroke in full, and the key distinction bears repeating here.

Heat exhaustion: sweating, pale, clammy, dizzy, nauseous — and mentally normal.

Heat stroke: confusion, aggression, disorientation, seizure, unconsciousness.

Any altered mental state in a hot person is heat stroke, it is a medical emergency, and cooling starts immediately without waiting for the ambulance.

The practical actions

Nine, and they are the whole of prevention.

Drink before you are thirsty. Thirst lags dehydration, particularly in older people. Water throughout the day, and an oral rehydration solution or salted drink if sweating heavily for hours.

Avoid the peak hours. **Roughly late morning to mid-afternoon. Shift outdoor work to early morning and evening — this is the single most effective measure for outdoor workers.

Find one cool place. **Even a few hours a day in a cooler environment substantially reduces risk. A public building, a mall, a library, a neighbour's room, a basement.

Cool the body directly. Wet cloths on the neck and wrists, a cool shower, wet clothing with air moving over it. Evaporation is the mechanism and a fan alone in very high temperatures with high humidity can be ineffective or worse.

Close the house during the day and open it at night. Curtains and shutters closed on the sunny side during the day; windows open when the outside temperature drops below the inside.

Wear loose, light, light-coloured clothing.

Eat lighter and more often.

Never leave anybody in a parked vehicle. The interior temperature rises to lethal levels within minutes, even with windows slightly open, and even on days that do not feel extreme.

And check on people. The most effective intervention in every heatwave review: somebody knocking on the door of an older person living alone, daily.

For outdoor workers

Because this is where the deaths concentrate.

Water, rest, shade — repeated on a schedule rather than when somebody feels bad.

Acclimatise. A person new to the work, or returning after a break, is at much higher risk for the first week or two, and this is a well-documented pattern.

Work in pairs and watch each other for confusion.

And the buddy check: a person with heat stroke does not know they have it. Somebody else has to notice.

Extreme cold

The critical fact

It does not require freezing temperatures.

Hypothermia happens at ten to fifteen degrees Celsius in wet and windy conditions, and most cases in temperate climates occur at temperatures people would describe as merely chilly.

Wet is the key variable. Water conducts heat away from the body roughly twenty-five times faster than air, which is why wet clothing is the single most dangerous condition (1.2, 7.2).

Who is at risk

Older people in under-heated homes — a very large cause of excess winter deaths, and it is about the cost of heating as much as about the weather.

People who are wet and outdoors.

People who have been drinking. Alcohol dilates blood vessels, increases heat loss, and removes judgement — and a substantial fraction of hypothermia deaths involve it.

Homeless people.

And infants, who lose heat fast and cannot shiver effectively.

The medical side

3.6 covers it. The signs, in order: shivering, then — as it worsens — shivering stops, coordination fails, speech slurs, and confusion appears.

The stopping of shivering is a bad sign.

**And the classic warning: the person insists they are fine, or begins removing clothing. Judgement goes early.

The practical actions

Eight.

Stay dry. **The most important. Change out of wet clothing immediately, even if it means being briefly colder.

Layers, not one thick garment. A base layer that moves moisture, an insulating middle, and a windproof and waterproof outer.

Avoid cotton next to the skin in cold conditions. It holds water and stops insulating — the reason for the mountaineering phrase that cotton kills.

Cover the head, hands and feet.

Get out of the wind. Wind strips heat far faster than still air at the same temperature.

Insulate from the ground. **Sitting or lying on cold ground takes heat much faster than air does. Anything between you and it — a mat, a bag, cardboard, branches.

Eat and drink warm things. The body needs fuel to generate heat, and cold suppresses thirst so dehydration is common in the cold.

And keep one room warm rather than the whole house, if heating is limited. Close the other doors, block draughts, and use the room with the fewest external walls.

At home in a cold snap

Heat one room. Wear layers indoors. Keep moving a little.

And the same intervention as heat: check on older neighbours. The excess winter death figures in every country are concentrated among older people living alone in cold homes, and a daily knock changes outcomes.

Never use an outdoor heater, generator, charcoal or gas appliance indoors for heat. Carbon monoxide poisoning during cold snaps and power cuts is a leading cause of death (6.2).

The common thread

Both hazards kill through slow physiological failure in people who are alone and unnoticed.

Which means the highest-value action in both is the same and it is not a piece of equipment.

It is somebody checking.

What to do with this page

Heat: drink before thirst, avoid peak hours, find one cool place, and never leave anybody in a vehicle.

Any confusion in a hot person is heat stroke. Cool immediately.

Cold: stay dry, layers, off the ground, out of the wind — and it does not need to be freezing.

Shivering stopping is a bad sign, and so is somebody insisting they are fine.

And in both: check on the older person living alone. It is the intervention that shows up in every review and it costs a knock on a door.

Next: 5.11 — drought, water and food security, the slowest of the crises and the one with the most preparation time.