42°C Outside. Here's the Science of How to Keep Your Home 5°C Cooler Without AC.

Delhi in summers is a nightmare. With temperatures touching 40–45°C this week and IMD warning that this summer will be harder than usual across a wide belt of north and central India, being practical about heat is not optional. For daily wage workers, students, elderly residents, and anyone who has to be outdoors, the stakes are real.

The Basics That People Know But Don't Follow

Drink water before you are thirsty.

This is the single most repeated and least followed piece of advice. By the time you feel thirsty in Delhi's summer heat, you are already mildly dehydrated. Your body loses water through sweat before your thirst signal catches up. Drink at least 3–4 litres of water through the day, more if you are outdoors.

Avoid the 11 AM to 4 PM window outdoors.

The UV index and ground-level heat are at their worst during this period. If your work or school requires you to be out during these hours, cover up (see below) and find shade whenever possible. Even five minutes of direct sun exposure on your head and neck during peak heat can trigger heat exhaustion in vulnerable individuals.

Don't wait for symptoms to act.

Heat illness develops faster than most people expect. If you feel dizzy, nauseous, stop sweating despite being hot, or feel confused — stop, find shade or an air-conditioned space, drink water, and call for help if symptoms do not improve in 15 minutes.

What to Wear

Cotton, loose, light-coloured, full-sleeved.

This sounds counterintuitive — more fabric in the heat? But loose cotton traps a layer of air next to the skin, which helps with evaporative cooling. Dark colours absorb heat. Light colours — white, beige, pale blue — reflect it. Traditional Indian clothing has this right: kurta-pyjama, salwar suits, and dupattas are all heat-adapted.

Cover your head outdoors.

The head and neck are the most heat-sensitive parts of the body. A cotton dupatta, cap, or umbrella makes a measurable difference. In very high heat, a wet cloth on the back of the neck can help bring temperature down quickly.

Protect your eyes.

UV-blocking sunglasses are not just a style choice in April. Prolonged UV exposure contributes to eye fatigue, which makes heat exhaustion worse. They also reduce the squinting and headaches associated with glare.

Avoid synthetic fabrics.

Polyester and nylon trap heat and prevent evaporation. On a 42°C day, wearing synthetic clothing is actively harmful.

Also Read: Delhi Just Hit 40°C Again — And IMD Says This Is Just the Warm-Up Act

What to Eat and Drink

ORS (Oral Rehydration Salts) — the underrated tool.

Plain water hydrates, but on a day of heavy sweating, your body is losing sodium, potassium, and other electrolytes along with water. Drinking only water can dilute your blood salts. ORS sachets — available at any chemist for ₹5–₹10 — restore this balance. You can also make a basic version at home: one litre of water, six teaspoons of sugar, half a teaspoon of salt.

Coconut water is genuinely good.

It is one of the better natural electrolyte drinks. It contains potassium, sodium, and magnesium — all lost during sweating. A tender coconut from a roadside vendor in Delhi in April is not just refreshing; it is functional nutrition.

Nimbu pani (lime water with salt and sugar) works similarly. Jaljeera is also useful. Traditional Indian summer drinks were designed for exactly these conditions.

Eat lighter meals. Large, heavy meals require more metabolic energy to digest, which raises body temperature. In peak summer, shift toward fruits (watermelon, cucumber, mango in moderation, muskmelon), curd, lassi, and lighter cooked food. Avoid very spicy or fried food during peak afternoon hours.

Mango: a note of caution- Mangoes are delicious and nutritious but they are also high glycaemic and heat-generating according to Ayurvedic tradition. Eating large quantities of mango in the hottest part of the day can worsen heat-related discomfort. Eat them in the morning or evening.

Avoid alcohol and carbonated drinks during peak heat. Both cause net fluid loss. Beer in the afternoon heat may feel refreshing but physiologically dehydrates you.

Also Read: Petrol Diesel Price Today April 18 2026 – Delhi, Mumbai, All States

Keeping Your Home Cooler Without an AC

Most Delhi households have fans but not air conditioning. Here are practical approaches that actually work:

Wet cloth or curtain trick. Hang a wet cotton cloth or sheet in a window that gets a breeze. As air passes through the wet cloth, evaporative cooling reduces the temperature of incoming air by 3–5°C. This is the principle behind a desert cooler — and it can be replicated manually.

Keep windows closed during peak heat, open at night. This is counterintuitive for people used to opening windows for air. In peak summer, the outside air between 11 AM and 5 PM is hotter than your room. Keeping windows shut with curtains drawn traps the relatively cooler indoor air. Open up once outdoor temperatures drop below room temperature — typically after 8 PM in Delhi.

Earthen matka (clay pot) water. Refrigerators cool water but not to the pleasantly cool temperature of a matka. Clay pots cool water through evaporation from their porous surface. The temperature of matka water sits around 20–22°C — cooler than room temperature but not as cold as a refrigerator, which means you can drink larger quantities without the shock of cold water.

Minimise heat-generating appliances. Ovens, pressure cookers running for long periods, high-wattage lighting — all generate heat inside the home. In peak summer, cook in the early morning, use LED lighting, and avoid running the dishwasher or washing machine during peak afternoon hours.

Plant a chameli or neem near your window if you can. Long-term, trees and plants reduce ambient temperature significantly. Neem trees in particular provide dense shade and are known to cool surroundings. This is not an instant fix but it is a generational one.

For Outdoor Workers: Construction, Auto-Rickshaw, Delivery, Vendors

The most at-risk people during a Delhi heatwave are those who have no choice but to be outdoors — construction workers, delivery riders, auto drivers, street vendors, and agricultural labourers on the city's fringes.

Practical steps for this group:

• Carry an insulated water bottle and refill it at every opportunity. Municipal water points and tap-filling stations exist in most Delhi markets.
• Work from shadow to shadow. Move between shaded spots, avoid standing directly in sun even briefly if possible.
• Apply damp cloth to wrists and forehead when resting. The wrists have surface veins close to the skin; cooling them helps lower overall body temperature.
• Recognise heatstroke in colleagues. If a coworker stops sweating despite extreme heat, becomes confused or unresponsive, or has hot and dry skin — this is a medical emergency. Move them to shade, apply water to the skin and fan them, and call an ambulance.

Employers at construction sites are legally required to provide shade, drinking water, and rest breaks for workers during extreme heat. Workers can report violations to district labour officers.

For Children and the Elderly

Children do not regulate body temperature as efficiently as adults. Keep children indoors during peak hours, ensure they drink water regularly (they often don't ask), and watch for unusual irritability, reduced urination, and flushed skin as early signs of dehydration.

For the elderly, heat stress can trigger cardiac events and is particularly dangerous in those with existing heart, kidney, or blood pressure conditions. Air-conditioned spaces — malls, libraries, metro stations — serve as informal cooling centres and can be life-saving. Many RWAs (Resident Welfare Associations) in Delhi have established informal cooling rooms in common areas during peak summer.

What Not to Do

• Do not drink cold water immediately after coming in from peak heat. It can cause throat cramps and digestive distress. Sit in the shade for 5–10 minutes first, then drink at room temperature.
• Do not apply ice directly to the skin during heat exhaustion. Rapid cooling can cause blood vessels to constrict. Use cool (not cold) water on the skin instead.
• Do not assume you are acclimatised. Even people who have lived in Delhi their whole lives can succumb to heatstroke. Physiological limits do not care about familiarity.

If You Suspect Heatstroke: The Emergency Protocol

• Move the person to a cool, shaded spot immediately
• Remove excess clothing
• Apply cool (not ice-cold) water to the skin, especially the neck, armpits, and groin
• Fan them continuously
• Give water or ORS if they are conscious and able to swallow
• Do not give paracetamol — it does not reduce heat illness body temperature
• Call emergency services (112) if body temperature stays high, person loses consciousness, or stops responding