Picture this: the sun beating down, asphalt radiating heat like an open-air oven, you running, sweat pouring in streams. In that moment, water isn’t just a neutral element — it’s practically a matter of survival. And yet, when it comes to staying hydrated during summer runs, plenty of myths and some dangerously casual advice still circulate.
Drink a lot? A little? Before, during, or after? Electrolytes: yes or no?
Thankfully, science can help clear things up. I’ve put together a handy little guide — based in part on the recommendations of the American College of Sports Medicine (ACSM). It’s not meant to be set in stone — after all, we each sweat and process fluids differently. But it’s a great starting point for building your own personalized hydration strategy (and if you’d like, you can share it with us afterward).
Here are the 10 science-backed rules for staying perfectly hydrated when running in the summer.
1. Start before you run
Waiting until you’re thirsty is a classic mistake. Start hydrating 1–2 hours before your run by drinking 5–7 ml per kg of body weight. In plain terms: for a 70 kg adult, that’s about 350–500 ml of water. This helps ensure you show up to your workout well hydrated.
2. Personalize your strategy
There’s no one-size-fits-all magic number here. It depends on how much you sweat, how long and intense your workout is, and what the temperature and humidity are like. The simplest way to find out how much fluid you lose? Weigh yourself (without clothes) before and after your run. Every kilo you lose roughly equals 1 liter of fluid you need to replace.
3. Pay attention to electrolytes
When you sweat, you lose not just water but electrolytes — mostly sodium, but also potassium, magnesium, and chloride. For long runs (>60 minutes) or very sweaty workouts, water alone isn’t enough: you’ll need a hypotonic or isotonic electrolyte drink (those with salt concentrations similar to those in your body). No, you don’t need to clear out the sports drink aisle: a well-balanced supplement or sports drink will do the trick.
4. Thirst isn’t a good guide
Thirst is reactive, not preventive. When you feel thirsty, you’re already moderately dehydrated. So get in the habit of sipping regularly — even if you don’t yet feel the urge.
5. How much should you drink during your run?
Roughly 400–800 ml of fluid per hour, depending on your sweat rate and the weather. But be careful: gulping too much at once can slow gastric emptying and make you uncomfortable. Small, frequent sips work best.
6. Skip the ice-cold water
I know — cold water is hard to resist in the summer. But if it’s too cold, it can cause cramping or slow digestion. Aim for cool, not icy (about 10–15 °C / 50–59 °F is ideal).
7. Don’t overdo the electrolytes either
The myth that “you always need electrolytes” is hard to kill. If your workout is short (<60 min) and low-intensity, plain water is perfectly fine. Adding electrolytes unnecessarily can actually cause imbalances.
8. Post-run? Yes, but smartly
After sweating it out, rehydrate gradually: about 120% to 150% of the weight you lost. If you lost 1 kg, aim to drink about 1.2–1.5 liters over the next 4–6 hours, in small sips. No, chugging a liter of water immediately after finishing isn’t the best plan.
9. Watch out for alcohol
Cold beer after a run? The romantic notion that “beer replaces salts” doesn’t hold up to scientific scrutiny. Alcohol is a diuretic — it increases fluid loss and slows recovery. If you really want one, go for it in moderation, and have water alongside it.
10. Listen to your body (but not only your body)
Learn to recognize signs of dehydration: early fatigue, decreased performance, dizziness, cramping. But don’t rely solely on how you feel — body weight and urine color (ideally light, pale yellow) are much more reliable indicators.
In short: hydrating for summer running isn’t dogma or religion. It’s a dynamic balance of science and self-awareness. Experiment, observe, adjust.
And remember: when you’re running under the blazing sun, sweat-soaked shirt clinging to your back, every sip of water is a small act of love for your body.