How much water should runners drink in hot weather in South Africa?
There is no single number: sweat rates range from about 0.5 to over 2 litres an hour. The best rule is to drink to thirst and check your own sweat rate by weighing yourself before and after a run. Aim to finish no more than about 2 to 3% lighter, and never heavier, which signals overdrinking.
- Sweat rates are commonly 0.5 to 2 L/h and can exceed 3 L/h; sweat sodium ranges roughly 10 to 90 mmol/L.
- The 2015 consensus supports drinking to thirst; about 3% body-mass loss is generally tolerable in cool-temperate conditions.
- Sweat loss (L) = weight lost (kg) + fluid drunk (L); gaining weight during a run suggests overdrinking.
- Electrolyte sachets cost roughly R4.63 to R20 each in South Africa (October 2026).
How much do runners sweat?
Sweat rates in athletes are commonly 0.5 to 2 L/h and can pass 3 L/h in hot, humid conditions such as a Durban summer or a Lowveld afternoon. Sweat sodium also varies several-fold (roughly 10 to 90 mmol/L). That is why a generic "drink 250 ml every 15 minutes" rule helps some runners and harms others.
What is the best rule: thirst or a schedule?
The 2015 hyponatraemia consensus supports drinking to thirst. It avoids both significant dehydration and overdrinking. A body-mass loss of about 3% is generally tolerable in cool to temperate conditions, and you should be wary of any weight gain during a run. See what is hyponatraemia.
How do you do a sweat-rate test?
- Weigh yourself nude (or in minimal, dry clothing) before a 60-minute run at race effort.
- Run, noting how much you drank.
- Towel off and weigh again.
- Sweat loss (litres) = weight lost (kg) + fluid drunk (litres) minus any toilet visits. One kilogram is about one litre.
Worked example: a 70.0 kg runner finishes at 68.8 kg after drinking 0.5 L. Sweat loss is 1.2 + 0.5 = 1.7 L/h. They replaced 0.5 L by thirst and lost 1.2 kg (1.7% of body mass) in an hour. At that pace they would cross 3% (2.1 kg) in under two hours, so a longer hot run needs more fluid, a slower pace, or both.
Repeat the test in hot and cool weather. Your numbers will differ.
What should you drink?
- Under about an hour: water is enough for most people.
- Over 1 to 2 hours, or heavy sweating: a drink with sodium, and carbohydrate if you are fuelling. See do I need electrolytes or just water.
- After the run: replace the deficit over the next few hours with fluid, food and some salt. The 2016 ACSM, Academy of Nutrition and Dietetics and Dietitians of Canada position suggests about 1.25 to 1.5 L per kilogram lost.
Electrolyte sachets cost from about R4.63 (Biogen Electrolyte) to R20 (Rehidrat) each in October 2026; see electrolyte costs in South Africa.
Hot-weather practicalities
- Acclimatise over 10 to 14 days; sweat rate rises and sweat gets less salty.
- Run in the early morning, in shade, with a cap and light clothing.
- Pale yellow urine through the day means you are broadly fine; dark urine means drink more.
- Heat stroke (confusion, collapse, hot dry or very sweaty skin) is an emergency: call 112 or 10177 and cool the person immediately.
Who needs different advice?
People with kidney, heart or blood pressure conditions, or on diuretics, should get medical advice on fluid and sodium targets. Children and teenagers should drink to thirst and eat normally, and pregnant runners should ask their doctor about training in heat.
Products mentioned, with dated prices
| Product | Size | Price | Servings | R per serving | Sweeteners |
|---|---|---|---|---|---|
| Biogen Electrolyte (3 x 10 sachets, citrus) | 3 x 10 sachets | R139–R155Dis-Chem (electrolytes group), Oct 2026 | 30 | R5.17 | Not published |
| Lifestyle Electrolyte Fizzy (10 tablets) | 10 effervescent tablets | R48–R53Dis-Chem (electrolyte drinks page), Oct 2026 | 10 | R5.30 | Not published |
| Biogen Active Hydrate (15 sachets) | 15 sachets | R180–R200Dis-Chem (energy and endurance category), Oct 2026 | 15 | R13.33 | Not published |
| USN Purefit Zero Sugar Hydrator (10 sachets) | 10 sachets | R100–R113Clicks via PriceCheck, Oct 2026 | 10 | R10.00 | Not published (zero sugar) |
Compare the options
Related questions
- What is hyponatraemia and how do runners avoid it in South Africa?
- Do you need electrolytes or is water enough?
- How do you stay hydrated training in summer heat in South Africa?
- How much sodium do you need per hour when running in South African heat?
- How do you make a homemade electrolyte drink in South Africa?
Sources
- Hew-Butler et al. 2015, Third International Exercise-Associated Hyponatremia Consensus Statement (BJSM 49:1432)
- Baker 2017, Sweating rate and sweat sodium concentration in athletes (Sports Med)
- Thomas, Erdman & Burke 2016, Position of the Academy of Nutrition and Dietetics, Dietitians of Canada and ACSM: Nutrition and Athletic Performance
Educational information only, not medical advice. Speak to a doctor, pharmacist or registered dietitian before using supplements if you are pregnant or breastfeeding, under 18, taking medication, or living with kidney, liver or heart disease.
Cite this page: Healthnews24, “How much water should runners drink in hot weather in South Africa?”, updated 27 October 2026, https://www.healthnews24.co.za/answers/how-much-water-should-runners-drink-in-hot-weather-south-africa/. Plain-text version: /answers/how-much-water-should-runners-drink-in-hot-weather-south-africa.md