Hot Weather Hydration: Tips for Staying Hydrated All Summer

When the weather warms up, good hydration is more important than ever. In this guide, you’ll learn how to stay hydrated in the heat.

It’s summertime and the warm weather’s here. For many of us, that means barbecues, outdoor fun, and days by the sea. 

While we generally love the season, it’s got certain downsides too. Perhaps the biggest is dehydration. In warmer weather, you sweat and exhale far more fluid than in colder conditions, and that can lead to some serious health hazards. 

According to the World Health Organization, you might lose as little as 500ml in sweat per day when resting in cool temperatures, but can lose twenty times as much (10 litres) on days when you exercise in the heat. Since human adults are about 50-60% water, topping up any lost liquid is absolutely critical.

So, it’s a good idea to plan how to keep hydrated in the heat. In this guide, you’ll learn:

• Why hot weather hydration is so important

• The best ways to keep hydrated in hot weather

• Additional hot weather hydration tips for exercise

Why is hot weather hydration so important?

We all know that it’s important to stay hydrated in hot weather. But it’s valuable to know exactly why this is. 

Here are some of the key reasons to keep slurping while it's scorching:

• Avoids heat-related sickness: Dehydration can increase your risk of a variety of conditions that range from uncomfortable to life-threatening. Heat cramps, heat exhaustion, and (most dangerous) heat stroke are all ones to avoid. 

• Reduces risks of other conditions: Keeping well-hydrated also reduces your risk of other unpleasant issues, such as kidney stones, UTIs, heart conditions, and constipation. 

• Focus and concentration: Even mild dehydration can significantly reduce your ability to focus, remember things, or use your psychomotor skills, according to studies. And it’s been reported that the effects of dehydration on your reaction times are equivalent to driving under the influence. 

How to stay hydrated in hot weather

According to the NHS, most people in temperate climates need between 1.5L and 2.5L of fluid per day. That can come from water, almost all non-alcoholic beverages, and your food. But in warmer conditions, you sweat and exhale more, so you will need to take on additional liquid to prevent dehydration. 

We’ve put together some general suggestions for hot weather hydration when you’re doing everyday activities (commuting, gentle walking, office jobs, housework, etc.). If you’re looking for hydration tips for hot weather exercise, we’ve provided additional ideas further down this page. 

Don’t wait until you’re thirsty

This is probably the golden rule of hot weather hydration. If you start feeling thirsty (sticky, dry mouth, mild headache, lightheadedness), it means you’re already dehydrated. Keep drinking water throughout the day to avoid getting to this stage. 

Start early

Even in the middle of a heatwave, mornings can be quite cool, so you might think it’s unnecessary to drink as much. However, there might be fewer opportunities to drink when you’re out and about later in the day. It’s just a lot easier to drink extra fluid at home in the morning. 

Little and often

In hotter weather, it’s best to drink little and often, rather than trying to chug down a litre every couple of hours. Aim for a glass of water every 20-30 minutes. 

Partly, this is because your body can absorb smaller quantities of water more efficiently. But it’s also because drinking large volumes of fluids in one go can lead to electrolyte imbalances (more on this below).

Track how much you’re drinking

If you’re busy, it’s easy to forget how much liquid you’ve actually consumed. A simple way to keep track is by using a sports bottle with measurements on the side.

Carry extra water with you

It’s easy to forget, but carrying extra fluid with you can make a huge difference. If you’re going out on a warm day, put a second bottle of water in your bag. You’ll thank yourself later.

Choose hydrating foods

When they’re thinking about how to stay hydrated in hot weather, people often forget about their food. But some kinds of meals can be super effective for hydration. Obvious contenders to pack in your lunchbox include fruit and veg with high water content (tomatoes, cucumbers, celery, and, of course, watermelon). Cold soups like gazpacho or things like Greek salad will also boost your fluids while filling you up. You could also try making frozen lollies with blended fruit and water. 

Keep an eye on your pee

The colour of your pee is one of the simplest ways to gauge your hydration. If it’s clear or a pale straw colour, you’re fine. But darker yellows through to orangey-red are a sign you’re low on fluids and need a top-up. 

Listen to your body

Your body will let you know if you’re heat-stressed. If you start getting headaches, cramps, light-headedness, or tiredness, these are all signs you need some of the wet stuff. 

Learn more: How to stay hydrated

Electrolytes and the problem of overhydration

If it’s hot out, the obvious solution is to drink gallons of water, right? Unfortunately, that’s not always the right approach. 

When you sweat, electrolytes (essentially salts) also get excreted. So, if you suddenly drink large amounts of water, the remaining salts in your body will be much more diluted. This can lead to a condition called hyponatremia. 

Hyponatremia can be pretty nasty. It causes vomiting, confusion, and - in very extreme cases - seizures, coma, or even death.

Does this mean you need to go out and buy sports drinks packed full of electrolytes? Not necessarily. Most people can get adequate salts from their regular diet. By drinking smaller quantities but more regularly, your body has time to balance salts and water. 

All the same, having a low-calorie drink containing electrolytes can be helpful, especially if you've been sweating more than usual. 

What are the best drinks to stay hydrated in the heat?

For most people, most of the time, water is the best drink for hydration in hot weather. Your body can absorb it extremely efficiently. It’s also basically free, contains no calories or sugar, and you’ve evolved to use it for many bodily functions. 

That said, most non-alcoholic drinks will also hydrate you effectively, since they are mainly made from water anyway. This includes:

• Squash

• Flavoured water

• Juice

• Milk

• Low/no sugar fizzy drinks

• Electrolyte drinks

Contrary to what you might have heard, tea and coffee are also good sources of fluids. While it’s true that caffeine is a diuretic (something that makes your pee more), the amount of water in most teas and coffees is still enough to hydrate you. 

Energy drinks are a different question. Consumed in moderation, some energy drinks are fine for hydration. However, they often contain very high levels of caffeine (more than in teas and coffees), so they may be more likely to dehydrate you. They may also contain more sugar and other chemicals. 

The big no-no is alcohol. While a cold beer or glass of rosé can certainly be appealing on a sunny day, it will dehydrate you. So, if you do choose to booze in the heat, take care to drink a glass of water with every alcoholic drink you consume.

Suggested: Should you exercise when you’re hungover?

How to stay hydrated in the heat when exercising

If you’re exercising or doing a manual job in the heat, then planning your hydration strategy is even more important. 

Studies by the American military have shown that, when exercising in warmer conditions, adult males can lose up to four litres of fluid per hour (though the average is closer to 1.5L). Replacing that fluid is essential if you want to train or work healthily. 

Here are some tips for hot weather hydration when you’re being active.

Consider calculating your sweat rate

This is more important for people who are taking part in competitive sports, but it can still be interesting for others. Your sweat rate is a measure of how much fluid you lose per hour when exercising. 

People have different sweat rates. Some sweat less, so they may not need to take on as much fluid. Others sweat more, so they need to make up for what’s pouring out of their pores. 

To figure out your sweat rate, you need to weigh yourself immediately before and immediately after working out. For example, say your main sport is cycling. Before a session, you weigh 65.5kg. After a 30-minute ride, you weigh 64.9kg. This means you lose 600g every 30 mins (or 1.2kg per hour). Therefore, at the very minimum, you should be drinking 1.2L of additional fluid in order to stay hydrated each hour. 

Do note that this is only a very rough guide. Factors such as temperature, altitude, humidity, exertion, and prior hydration levels will all influence your sweat rate.

Pre-hydration is critical

By drinking adequate amounts of water before your workout begins, you reduce your chances of becoming dehydrated in the first place (pre-hydration is also known to improve performance). Try to drink at least half a litre of water in the hour before training begins. 

Don’t skip the hydration station

You should aim to drink little and often when exercising or working in the heat. The UK’s Health and Safety Executive says people doing active jobs in hot conditions should have about 250mL of water every 15 minutes. Whether you’re working on a summer building site or training for a marathon, it’s so important to keep topping up. 

Try using sports drinks

Sports drinks can be a good choice when you’re exercising in hot weather. They contain electrolytes, which replenish any salts you lose through sweat. Choose products from reputable brands and avoid those that contain large quantities of sugar or caffeine. 

Post-exercise hydration

Remember to keep replenishing your fluids in the hours after your training too. People tend to sweat more than usual for up to 60 minutes after exercise, and this is only exacerbated by warm weather. 

Related: 6 tips for working out in hot weather

The importance of knowing how to keep hydrated in the heat

While everyone knows that hot weather hydration is essential, this doesn’t always translate into action. For example, one survey in the UK found that the average person drinks less than half the recommended daily amount of water. 

By knowing how to stay hydrated in hot weather, you can build strategies to keep yourself healthy and comfortable, and ready for the next heatwave.