You already know the drill: "drink 1.5 liters of water per day, especially in summer." But when Brussels terraces hit 34 degrees, you spend two days at a festival, or you run at 7 p.m. because you couldn’t find an earlier slot, the 1.5-liter rule is no longer enough.
Not at all. This article covers everything from the start: what happens in your body when it’s hot, the signals 90 percent of people ignore, how much to really drink, and especially when plain water becomes insufficient. No medical jargon, no generic lists. Just what works.
Why summer completely changes the game for your hydration
When it’s hot, your body loses not only water. It also loses salt, potassium, and magnesium through sweat. That’s why after a heavy sweating session you can feel dizzy even if you drink a lot of water. You’ve replaced the water but not the minerals that go with it. The result: your body can’t properly absorb the fluid you just drank, and some of it goes straight to the bathroom.
This is the real issue with summer hydration. Not how much you drink, but what you drink and how your body uses it. A person who sweats a lot and drinks only water can end up feeling more tired than before because the mineral concentration in their blood drops. English speakers call this hyponatremia, and it happens more often than you think, especially among amateur runners who keep drinking bottles of plain water without ever thinking about electrolytes.
Signs that show you are already dehydrated
Dehydration doesn’t warn you. When you feel thirsty, you’ve already lost about 1 to 2 percent of your body weight in water. In other words, you’re late.
Obvious signals not to ignore
Dry mouth, rare urge to urinate, very dark urine, thirst that becomes constant. Everyone knows these. Add to that the feeling of heat that doesn’t go down when you go indoors, and you have the classics.
Less known signals that fool everyone
Headache at the end of the day when you haven’t done anything special. Fatigue setting in around 3 or 4 p.m. for no apparent reason. Difficulty concentrating on work or a conversation. Night cramps in the calves. Mood swings, easy irritability. These signals often point to mild chronic dehydration, the kind that doesn’t land you in the hospital but ruins your days without you making the connection. If you check two or three of these during a heatwave, you have your answer.
How much to really drink when it’s hot
The 1.5-liter rule is a universal minimum, not a target for everyone. A sedentary adult in Belgium in July will need about 2 to 2.5 liters of liquid per day. As soon as you add physical activity, even moderate like a one-hour bike ride, you should count 500 ml to 1 liter more. If you do intense sports or stay in the sun for a long time, you can easily reach 3 to 3.5 liters in a day.
Simple tip to measure without calculating: look at the color of your urine in the middle of the day. If it’s pale yellow like light straw, you’re good. If it’s dark yellow like tea, you’re behind. Clear white means you’ve probably drunk too much pure water and diluted your minerals, which isn’t ideal either.
And don’t forget: liquid doesn’t come only from water. A cup of tea, a bowl of cold soup, a yogurt, a watermelon—all count toward your total. Seasonal fruits and vegetables easily cover 20 percent of your daily hydration needs when you eat enough of them.
When plain water is no longer enough and why
Here’s the point no one clearly explains to you. Plain water does the job for a normal day working from home with air conditioning. As soon as you step outside that frame, it shows its limits. Specifically, water becomes insufficient when you sweat for more than 30 minutes straight, when the temperature exceeds 28 degrees in the shade for several hours, or when you do a big physical effort.
What’s missing at these times is the trio potassium, magnesium, and sodium. These three minerals are responsible for transporting water into your cells, nerve transmission, and muscle contraction. Without enough of them, your body doesn’t know what to do with the water you give it. That’s why electrolytes matter: they reset the counters and allow hydration to really happen.
This is exactly the role played by BUDDY sticks. Potassium, magnesium, sea salt, soluble fibers, no sugar, two flavors (Mint Lemon and Citrus Peach), to dissolve in a water bottle. You don’t replace your water, you make it usable by your body. It’s the difference between swallowing gasoline without an engine and swallowing gasoline in a car.
Drinks to avoid in summer even if they seem refreshing
Not all cold drinks hydrate. Some even make things worse. Regular sodas contain 25 to 35 grams of sugar per can, which calls for extra water to be metabolized. You drink to compensate for a loss, and you actually create an additional loss.
Alcohol is clearly the number one enemy in summer. Diuretic, it sends you to the bathroom faster than you absorb it, and rough mornings during heatwaves rarely have another explanation. That doesn’t mean you have to ban terrace aperitifs, it means you should double every glass with a bottle of water to stay afloat.
Iced coffee in excess, same fight in a lighter version. Mild diuretic, it makes you lose a bit more fluid than it provides. One or two a day, no problem. Six, and it’s a one-way ticket to a headache at 5 p.m.
And be especially wary of "hydrating" drinks marketed as such on supermarket shelves. Some contain as much sugar as a Coke, under a sporty image. Read the labels. If you see more than 5 grams of sugar per 100 ml, move on.
Good concrete habits to adopt right now
Here’s the actionable summary we wish we had before every summer.
Start your day with a large glass of room temperature water before coffee. Your body loses 300 to 500 ml overnight, catch up.
Keep a 750 ml or 1-liter bottle always within reach. On your desk, in your bag, in the car. Visual constraint does 80 percent of the work.
When you exercise in hot weather, add an electrolyte stick to your bottle. Once you’ve tried it once, you won’t go back. The recovery difference is clear.
For festivals, plan a stick in the morning on waking, one in the late afternoon, one before sleeping. Couleur Café, Dour, Tomorrowland, the rule is the same: you dance eight hours under 32 degrees, you can’t expect to hold up with beer and three sips of water.
During heatwaves, eat water-rich fruits and vegetables at every meal. Cucumber, watermelon, tomato, melon, zucchini. They are your silent allies.
Listen to your fatigue. If you feel an unexplained slump in the middle of the afternoon, try a glass of water with electrolytes before rushing to coffee. Nine times out of ten, that’s what was missing.
Summer hydration FAQ
How many liters of water per day during a heatwave
Count 2 to 3 liters of total liquid per day for a normal adult, and up to 4 liters if you combine heatwave and physical activity. No need to be exact, but clearly go above the usual 1.5 L.
Are electrolytes useful if I don’t exercise
Yes, as soon as you sweat a lot: heatwave, crowded metro ride, terrace in the sun all afternoon, festival, long car trip without air conditioning. You don’t need to be a marathon runner to lose minerals.
Can you rehydrate by eating fruit
Partly yes. Watermelon, cucumber, strawberry, and melon are over 90 percent water and also contain potassium. They complement your hydration but don’t fully replace what you drink, especially in strong heat.
Does sparkling water hydrate as well as plain water
Yes, hydration is the same. The difference is only in digestive comfort (some people bloat with sparkling) and the sodium content of some sparkling waters which can be high. For daily hydration, plain or sparkling is your choice.
Take action without overthinking it
This summer, stop improvising your hydration. A bottle of water, an electrolyte stick when you sweat, fruits at every meal, and a real look at your urine color in the middle of the day. It’s that simple.
If you want to try BUDDY sticks without breaking the bank, the Starter Pack gives you 20 sticks and a dedicated bottle for 45 euros. Mint Lemon and Citrus Peach, no sugar, with potassium, magnesium, and sea salt. You’ll see the difference from the first hot day.
And if you’re looking for a natural boost, check out the Buddy cans, natural and organic caffeine, 13 kcal per 100 ml, which go well with long days without the sugary junk of classic energy drinks.
Summer is already here, so live it properly hydrated.
