Staying hydrated in hot weather: an Indian summer guide

Why you need more when it’s hot

The usual intake figures assume moderate temperatures and activity — Europe’s food safety authority, EFSA, says so explicitly. India’s dietary guidelines note that the everyday two litres or so goes up during very hot weather and vigorous physical activity.

What India’s heatwave advisory says

The Ministry of Health & Family Welfare’s 2026 advisory on extreme heat advises:

• “Drink sufficient water whenever possible, even if you are not thirsty. Thirst is not a good indicator of dehydration.”
• Carry drinking water when you travel.
• Use oral rehydration solution (ORS), and homemade drinks like lemon water, buttermilk or lassi, and fruit juices with some added salt.
• Eat seasonal fruit and vegetables with lots of water in them: watermelon, muskmelon, oranges, grapes, pineapple, cucumber.
• Avoid alcohol, tea, coffee and fizzy or very sugary drinks, which it says “actually, lead to loss of more body fluid or may cause stomach cramps”.

For workplaces, it asks employers to provide cool drinking water and to remind workers to drink a cup of water every 20 minutes or more often.

How much is too much?

More isn’t always better. US workplace-safety guidance (NIOSH) for people doing physical work in the heat suggests about a cup — 8 ounces, roughly 240 ml — every 15 to 20 minutes, and no more than about 1.4 litres an hour. That’s for sweating through hard work, not for a day at a desk. Drinking far more than you need can dilute the sodium in your blood (hyponatremia), which can be life-threatening.

Who needs extra care

The advisory singles out infants and young children, people working outdoors, pregnant women, people with a mental illness, and people who are physically ill, especially with heart disease or high blood pressure. Travellers arriving from a colder place should give their bodies about a week to get used to the heat, and drink plenty of water.

Habits for hot days

• Start the day with a glass, and keep a bottle with you whenever you go out.
• Drink on a schedule rather than waiting to feel thirsty.
• On the hottest days, swap the afternoon tea or cold drink for plain water, buttermilk or lemon water.
• Keep an eye on your pee: pale is good; dark yellow means catch up.
• Know the warning signs of heat stress: dizziness or fainting, nausea or vomiting, a headache, extreme thirst, less pee that is unusually dark, and fast breathing and heartbeat. If they appear, move somewhere cool, drink — water is best — and get medical help.
• Call 112 at once for anyone with a high temperature who is unconscious, confused or has stopped sweating.

More on the signs to watch for: signs you’re not drinking enough water.