Training in Hot Weather: A Summer Hydration and Electrolytes Guide
Training in hot weather is harder because your body has to cool itself and supply your muscles with blood at the same time, so your heart works harder and you lose more fluid through sweat. To train safely in summer, pick cooler times of day, build up gradually over 1 to 2 weeks, drink to a plan before, during and after sessions, and use electrolytes when sessions are long, hard or very sweaty. If anyone shows signs of heatstroke, such as confusion or collapse, call 000.
Melbourne summer weather can change quickly, so a plan helps. Here is how heat affects training, the warning signs to know, and how to handle hydration for exercise and electrolytes in summer.
Why heat makes training harder
To shed heat, your body sends more blood to your skin and you sweat more. Your heart is now supplying both your muscles and your skin, which adds strain.
Sweat cools you as it evaporates. On humid or still days, sweat does not evaporate as well, so heat stress can be higher than the temperature alone suggests. Dehydration in the heat adds to that strain.
Fluid loss matters too. Sports Dietitians Australia defines dehydration as a fluid deficit of more than 2% of body mass, and expert consensus links deficits above about 2% with reduced performance. For a 75 kg person, that is around 1.5 kg.
Sports Medicine Australia's Extreme Heat Risk and Response Guidelines look at temperature, humidity, sun, wind, the type of sport and the clothing worn. Their free heat risk web tool rates the risk for your sport and postcode.
Warning signs of heat illness and what to do
Heat exhaustion and heatstroke are different. Here is a simple comparison based on healthdirect.
| Sign | Heat exhaustion | Heatstroke |
|---|---|---|
| Body temperature | Normal or slightly high | Above 40°C |
| Skin | Cool, pale and clammy | Red, hot or dry |
| Sweating | Usually heavy | Reduced or stopped |
| Other signs | Weakness, dizziness, headache, nausea | Confusion, slurred speech, poor coordination, seizures, collapse |
| What to do | Stop, rest somewhere cool, drink water or an electrolyte drink | Call 000 and start cooling straight away |
If you suspect heatstroke, call triple zero (000). While you wait, move the person into shade or a cool room, loosen extra clothing, and cool them with water spray, wet towels and a fan, or cold packs. Give small sips of cool fluid only if they are conscious. If they are unconscious, place them on their side and be ready to start CPR.
For heat exhaustion, healthdirect advises resting in a cool place and drinking water, an electrolyte sports drink or an oral rehydration solution. Call 000 if the person feels faint or confused, cannot drink, or has a seizure.
Risk is higher for older adults, pregnant people, people with heart or kidney conditions, anyone recently sick with a fever, and people on medicines that affect sweating. If that is you, check with your doctor before training hard in the heat.
Practical tips: time your sessions
Better Health Channel advises moving strenuous activity to a cooler time of day during extreme heat. Early morning or evening sessions usually work best. Check the Bureau of Meteorology forecast before you head out. On very hot days, train indoors.
Practical tips: build up over 1 to 2 weeks
An international consensus statement recommends heat acclimatisation through repeated exercise in the heat over 1 to 2 weeks, with most adaptations happening in the first week. Keep your first hot sessions shorter and easier, then build up.
Drink to a plan: before, during and after
- Before: start sessions well hydrated. Better Health Channel suggests drinking water before you feel thirsty, especially when you are active outdoors.
- During: take regular drinks, and add breaks in shade on hot days. Sports Medicine Australia suggests more frequent or longer rest breaks as heat risk rises.
- After: replace what you lost. See the weighing method below.
Weigh yourself to estimate sweat loss
Sports Dietitians Australia recommends weighing yourself in minimal clothing just before training, then again straight after, once you have towelled off. The difference is mostly fluid, and 1 kg is roughly 1 litre.
Their guidance is to replace 125 to 150% of that loss over the next 2 to 6 hours. So if you lose 1 kg, aim to drink about 1.25 to 1.5 litres. You need more than you lost because some of what you drink is passed as urine.
When electrolytes help and when water is enough
Electrolytes are not needed for every session. Sports Dietitians Australia says water is an excellent choice for low intensity and short sessions, while sports drinks suit high intensity stop-go sports and endurance training.
Sodium is the electrolyte to look for. Sports Dietitians Australia notes it helps you drink more by stimulating thirst, and it reduces how much fluid you lose as urine after exercise. The heat consensus statement suggests drinks with sodium for exercise lasting longer than an hour.
Electrolytes are more likely to help if:
- your session runs longer than about an hour
- you are doing hard, stop-go training such as team sports, HIIT or circuits
- you sweat heavily or lost a lot of weight during the session
- you are rehydrating after a big sweat loss
Browse the hydration and electrolytes range, or read our guide to the best electrolytes in Australia to compare sodium content, sugar and flavours.
Caffeine and pre-workout in the heat
The International Society of Sports Nutrition position stand says doses of 3 to 6 mg per kg of body mass have consistently improved performance, and that most research finds caffeine does not significantly impair hydration.
Side effects rise with the dose, so in summer:
- Count all your caffeine, including coffee and energy drinks.
- Stick to the serve on the label, and go lighter on hot days if you are new to a product.
- Do not use caffeine to push through feeling dizzy or unwell in the heat. Stop and cool down.
- Consider a stim-free pre-workout for hot days or evening sessions.
Our guide on which pre-workout is best explains the main types. If you are pregnant, take medication or have a heart condition, check with your doctor before using caffeine-containing products.
Your summer training kit list
- A large water bottle and a shaker for electrolytes (see our gym accessories)
- Electrolyte powder or tablets for longer and harder sessions
- SPF 50 or 50+ broad-spectrum, water-resistant sunscreen. Cancer Council advises reapplying every two hours or after heavy sweating
- A hat and sunglasses for outdoor sessions
- Light, breathable clothing
- A towel you can wet to cool your neck during breaks
- Bathroom scales at home to check sweat loss
How Supps247 can help
Pop into one of our 17 Victorian stores or our Richlands store in Brisbane to compare electrolytes. Our team can help you read labels and compare sodium and sugar, and you can try flavours in store. Find your nearest store with our store locator.
Or order online for click and collect or Australia-wide delivery (see shipping information). New to supplements? Try our beginners supplements guide.
FAQs
How much water should I drink when training in hot weather?
It depends on the heat, humidity, your effort and your body. Weigh yourself before and after a session. Each 1 kg lost is roughly 1 litre of fluid, and Sports Dietitians Australia suggests replacing 125 to 150% of that over the next 2 to 6 hours.
Do I need electrolytes or is water enough?
For short, low intensity sessions, water is usually enough. Electrolytes or a sports drink make more sense for hard stop-go training, sessions longer than about an hour, very sweaty days and recovery after a big sweat loss. Sodium helps you drink more and hold on to the fluid you drink.
How long does it take to get used to training in the heat?
Expert consensus says heat acclimatisation should involve repeated training in the heat over 1 to 2 weeks. Most of the changes happen in the first week.
Is it safe to take pre-workout in hot weather?
Most research finds moderate caffeine does not significantly impair hydration, but side effects rise with the dose. Keep your total caffeine moderate, or try a stim-free option. If you feel unwell in the heat, stop, cool down and rehydrate.
What are the signs of heatstroke during exercise?
Warning signs include a body temperature above 40°C, hot red or dry skin, reduced sweating, confusion, slurred speech, poor coordination, seizures or collapse. Heatstroke is a medical emergency. Call triple zero (000) and start cooling the person while you wait.
Sources: Sports Medicine Australia, Extreme Heat Risk and Response Guidelines 2025; SMA Extreme Heat web tool; healthdirect, Heatstroke; Better Health Channel, Extreme heat fact sheet; Racinais et al., Consensus recommendations on training and competing in the heat, BJSM 2015; Sports Dietitians Australia, Fluids in sport; Sports Dietitians Australia, Why is hydration important; ISSN position stand: caffeine and exercise performance (2021); Cancer Council, Be SunSmart.
