To stay hydrated in hot weather, drink regularly through the day rather than waiting until you’re very thirsty, carry water with you, eat water-rich foods such as fruit, salad and yogurt, and drink more when you’re active or sweating. Pale yellow pee is a good sign you’re drinking enough. The NHS heatwave advice is to drink extra fluids, have regular cold drinks, and limit alcohol. Older adults, babies, young children and people with long-term health conditions need the most care.
How much should you drink when it’s hot?
There’s no single number, because needs depend on your size, how active you are and how much you sweat. As a starting point, the NHS suggests 6 to 8 glasses of fluid a day in a temperate climate, and more in hot weather, during exercise and when you’re unwell. The European Food Safety Authority sets adequate total water intakes of about 2.0 liters a day for women and 2.5 liters for men, including the water in food (EFSA). In a heatwave, especially if you’re outdoors, you’ll usually need more than that.
Our guide to how much water to drink a day explains the different recommendations in more detail.
If you work or exercise in the heat
For people working outdoors, the US National Institute for Occupational Safety and Health (NIOSH) recommends:
- About 1 cup (240 ml) of water every 15 to 20 minutes during moderate activity in the heat lasting under 2 hours.
- Sports drinks with electrolytes if you’re sweating for several hours.
- No more than 6 cups (about 1.4 liters) an hour. Drinking far more than you sweat can dilute the sodium in your blood, which is dangerous.
Signs you’re getting dehydrated
The NHS lists these early signs:
- Feeling thirsty
- Dark yellow, strong-smelling pee, or peeing less than usual
- Feeling dizzy or lightheaded
- Feeling tired
- A dry mouth, lips and tongue
In babies, a sunken soft spot on top of the head and fewer wet nappies are warning signs. If you notice these, drink more straight away. If you’ve been sick or feel sick, start with small sips and build up.
Good drinks in hot weather
| Drink | Good for | Watch out for |
|---|---|---|
| Water, still or sparkling | Everyday hydration | Nothing; add lemon, cucumber or mint for flavor |
| Milk | Hydration plus protein and calcium | Choose lower-fat versions most of the time |
| Tea and coffee | Count toward your fluid intake | Large amounts of caffeine |
| Oral rehydration solution | Replacing fluid and salts after diarrhea, vomiting or heavy sweating | Follow the pack instructions |
| Sports drinks | Long sessions of heavy sweating | Sugar; not needed for everyday activity |
| Fruit juice and smoothies | Some vitamins | Free sugars; the NHS suggests 150 ml a day at most |
| Sugary soft drinks | Little | High sugar, extra calories |
| Alcohol | Nothing | Makes you pee more and worsens dehydration |
The NHS heatwave page advises limiting alcohol, caffeine and hot drinks when it’s very hot, while its general drinks advice counts tea and coffee toward your fluid intake. In practice, a normal cup of tea or coffee is fine, but don’t rely on strong coffee or energy drinks to stay hydrated. Our guide to calories in alcohol covers why alcohol and heat don’t mix well.
Eat your water too
Food supplies about 20% to 30% of the water we take in, according to EFSA. Many fruits and vegetables are more than 90% water, based on USDA FoodData Central values:
| Food | Water content |
|---|---|
| Cucumber (peeled) | 97% |
| Lettuce | 96% |
| Celery | 95% |
| Tomatoes | 95% |
| Watermelon | 91% |
| Strawberries | 91% |
| Cantaloupe melon | 90% |
| Plain yogurt | 88% |
| Oranges | 87% |
Cold salads, fruit, gazpacho and yogurt-based dishes are refreshing in the heat and add to your fluid intake. Fruit and vegetables also contain potassium, one of the minerals lost in sweat.
Practical habits that help
- Start the day with a drink, and have one with every meal and snack.
- Carry a reusable bottle and refill it often.
- Drink before, during and after exercise, and exercise in the cooler early morning or evening.
- Keep drinks cold. Cold water is more appealing, so you’ll drink more.
- Set reminders if you tend to forget, especially if you’re busy or work at a desk.
- Check your pee color. Pale straw yellow is the goal.
- Stay out of the heat where you can: the NHS advises keeping in the shade between 11am and 3pm.
Who needs extra care?
The NHS lists these groups as most at risk in a heatwave:
- Older adults, especially over 65. Thirst can be weaker with age, so drinking by habit matters more than waiting to feel thirsty. Our guide to healthy eating for older adults has tips on drinking enough.
- Babies and young children, who can’t always tell you they’re thirsty. Offer drinks often. Breastfed babies may want to feed more often in hot weather.
- People who are pregnant.
- People with long-term conditions, such as heart or kidney disease, diabetes, or dementia.
- People taking several medicines, or medicines that make you pee more (diuretics).
If your doctor has told you to limit fluids, for example because of heart failure or kidney disease, don’t increase your drinking without asking them first. They can tell you how to adjust in hot weather.
Heat exhaustion and heatstroke
Dehydration and heat often go together. The NHS describes heat exhaustion as feeling or being sick, heavy sweating with pale, clammy skin, cramps in the arms, legs and stomach, a high temperature, feeling very thirsty and feeling irritable.
What to do: move the person somewhere cool, remove unnecessary clothing, give them plenty of water to drink (a sports drink or oral rehydration solution also helps replace lost salt), and cool their skin by spraying or sponging it with cool water and fanning them. Stay with them. They should start to feel better within 30 minutes.
Heatstroke is an emergency. Call your local emergency number if someone is still unwell after 30 minutes of cooling, has hot skin that isn’t sweating, a fast heartbeat or fast breathing, is confused or uncoordinated, has a fit, or loses consciousness. While you wait, cool them with a cool, wet sheet, sponging or a fan.
Common questions
Is sparkling water as hydrating as still water?
Yes. It hydrates just as well. Choose unsweetened versions.
Do I need electrolyte drinks in hot weather?
Not for normal daily life. Food usually replaces the salts you lose. They’re useful after several hours of heavy sweating, or after vomiting or diarrhea. If you follow a low-carb diet, see our guide to keto electrolytes.
Can you drink too much water?
Yes, though it’s rare. Drinking very large amounts quickly, far more than you’re sweating, can lower blood sodium. Spread drinks through the day and stay under about 1.4 liters an hour.
This article is general information, not medical advice. Talk to your doctor or a registered dietitian before making big changes to how you eat, especially if you have a health condition, take regular medication, or are pregnant or breastfeeding.
