Heat exhaustion and heatstroke sit on the same spectrum of heat-related illness. Heat exhaustion is the milder stage, where the body is overheating but still coping, causing heavy sweating, dizziness, headache and tiredness. If it is not managed, or if the body can no longer control its temperature, it can progress to heatstroke, a medical emergency marked by confusion, hot skin and collapse. In Singapore’s hot, humid climate, both are common during outdoor work, sport and national service. Cooling and rest usually settle heat exhaustion; heatstroke needs 995 and rapid cooling.
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In a medical emergency, or for severe or sudden symptoms such as breathing difficulty, chest pain, fainting or stroke signs, call 995 immediately.
Singapore is warm and humid all year round, and high humidity makes it harder for sweat to evaporate and cool the body. This puts people who exert themselves outdoors, as well as the very young and the elderly, at real risk of heat-related illness. Recognising the difference between heat exhaustion and heatstroke, and acting quickly, can save a life. This guide explains the warning signs, first aid and how to stay safe in the heat.
What heat exhaustion and heatstroke are
Heat-related illness happens when the body absorbs or produces more heat than it can lose. Normally the body cools itself by sweating and by sending blood to the skin, but in hot, humid or hazy conditions, or during heavy exertion, these mechanisms can become overwhelmed.
Heat exhaustion is the earlier stage. The body is overheating and under strain, but it is still able to cope, and the person usually remains conscious and sweating. It is a warning sign that the body needs to cool down and rest.
Heatstroke is the dangerous, life-threatening stage. Here the body can no longer control its own temperature, and the core temperature climbs to a harmful level. This can affect the brain and other organs, which is why confusion and collapse are such important warning signs. Heatstroke is always a medical emergency.
Heat exhaustion — symptoms
Heat exhaustion tends to come on gradually and may include:
- Heavy sweating and pale, clammy skin
- Feeling faint, dizzy or lightheaded
- Headache
- Nausea or vomiting
- Tiredness or weakness
- Muscle cramps, often in the legs, arms or abdomen
- A fast pulse and fast breathing
- Feeling very thirsty
A key feature is that the person is usually still sweating and remains alert and able to respond. With cooling, rest and fluids, most people recover within a short time. If the symptoms do not improve, or if the person becomes confused or stops sweating, treat it as heatstroke.
Heatstroke — the danger signs
Heatstroke can develop from untreated heat exhaustion, or come on rapidly during intense exertion in the heat. Warning signs include:
- A very high body temperature and skin that feels hot to the touch, which may be dry or, especially with exertion, still sweaty
- Confusion, agitation or unusual behaviour
- Slurred speech
- Seizures
- Fast breathing and a fast, pounding heartbeat
- Loss of coordination or collapse
- Drowsiness or loss of consciousness
Any change in how a person is thinking, speaking or behaving in the heat is a red flag. This is an emergency — call 995 and begin cooling immediately.
Who is at higher risk
Anyone can develop heat-related illness, but the risk is higher for:
- Outdoor workers such as those on construction sites, in landscaping or on the roads
- Athletes and anyone doing strenuous exercise, including national service training and competitive sport
- Infants and young children, whose bodies heat up quickly
- Older adults, who may sense heat and thirst less well
- People with certain long-term illnesses, such as heart or kidney conditions
- People taking some medicines that affect sweating, hydration or heat regulation
- Anyone who is unwell, dehydrated, or has had alcohol
Hot, humid or hazy days raise the risk for everyone, particularly during the middle of the day when it is hottest.
First aid
For heat exhaustion:
- Move the person to a cool, shaded or air-conditioned place
- Help them lie down and raise their legs slightly
- Remove any excess or tight clothing
- Cool the skin with cool water, wet cloths or a cool shower, and fan them
- Give them water to sip, or a rehydration drink if available
They should start to feel better within a short while. If they do not improve, or if they worsen, become confused or lose consciousness, treat it as heatstroke.
For suspected heatstroke:
- Call 995 immediately
- While waiting, move the person into shade or indoors
- Remove outer clothing
- Cool them aggressively — pour or spray cool water over the skin, apply wet cloths, and fan continuously; immerse them in cool water if it is safe and possible
- If they are unconscious and not breathing normally, be ready to give CPR and follow the emergency operator’s instructions
Do not try to give fluids to someone who is drowsy, confused or unconscious, as they may choke.
How heatstroke is treated
Heatstroke is treated in hospital as an emergency. The priority is rapid cooling of the body to bring the temperature down as quickly as possible, using methods such as cool water, cooling equipment and fluids given into a vein. Doctors will monitor the heart, breathing, kidneys and other organs, check for complications, and provide supportive care. The sooner cooling begins — ideally at the scene while help is on the way — the better the outcome, which is why early recognition and first aid matter so much.
Prevention in Singapore’s climate
Simple habits go a long way in a hot, humid country:
- Stay hydrated. Drink water regularly through the day, before you feel thirsty, especially when active outdoors.
- Pace activity and rest. Take regular breaks in the shade or a cool place during exertion, and stop if you feel unwell.
- Acclimatise. Build up gradually to strenuous activity in the heat rather than starting hard, and be extra careful early in a training programme.
- Avoid the hottest part of the day. Where possible, schedule heavy work and exercise for cooler morning or evening hours.
- Dress for the heat. Wear light, loose, breathable clothing and a hat, and use shade.
- Check on vulnerable people. Look in on young children, older relatives and anyone unwell during hot or hazy weather.
- Never leave a child or pet in a parked vehicle, even briefly — the temperature inside can rise dangerously fast.
When to seek emergency help
Call 995 straight away if a hot person is confused or behaving strangely, is drowsy or unconscious, has a seizure, has hot skin and has stopped sweating, or has collapsed. Also seek urgent medical help if someone with heat exhaustion does not improve after cooling and rest, keeps vomiting, or cannot keep fluids down. When in doubt in the heat, treat the situation as serious and get help early — cool the person while you wait.
Common questions
What is the difference between heat exhaustion and heatstroke?
Heat exhaustion is the milder stage: the person is overheating but still coping, usually sweating and alert, with symptoms like dizziness, headache and tiredness. Heatstroke is a life-threatening emergency in which the body can no longer control its temperature, causing confusion, hot skin and collapse. Heatstroke needs 995 without delay.
What drinks should be avoided in the heat?
Avoid alcohol and very sugary drinks when you are hot or exerting, as they are less helpful for rehydration and alcohol can worsen fluid loss. Plain water is best for most situations, with an oral rehydration drink useful during prolonged or heavy activity. If you have a medical condition that limits fluids, follow your doctor’s advice.
Can heat exhaustion turn into heatstroke?
Yes. Untreated heat exhaustion can progress to heatstroke, particularly if the person keeps exerting themselves in the heat. This is why it is important to stop, cool down and rest at the first warning signs, and to seek help if there is no improvement.
Is it safe to exercise outdoors in Singapore’s heat?
It can be, with sensible precautions. Hydrate well, acclimatise gradually, take breaks in the shade, avoid the hottest hours, and listen to your body. Stop and cool down if you feel dizzy, unusually tired or unwell, and never push through symptoms of heat illness.
How can I tell if someone has stopped being able to cope with the heat?
The most important warning signs are changes in the brain and behaviour — confusion, agitation, slurred speech, drowsiness, seizures or collapse in someone who is very hot. If you see any of these, call 995 and cool the person aggressively while waiting.
Related guides
Sources
- HealthHub
- Health Promotion Board
- Singapore Sport Institute
- NHS