Quick answer

Heat exhaustion: pale, clammy, sweating heavily, weak and dizzy. Move them somewhere cool, lie them down, give cool fluids. They should improve within about 30 minutes. Heatstroke: skin red, hot and often dry, sweating may have stopped, and they are confused, slurring, uncoordinated or unconscious, with a body temperature above 40°C. That is a life-threatening emergency — call Triple Zero (000) and start cooling them immediately.

Confusion is the line. If someone who has been in the heat stops making sense, cannot answer you properly, is slurring or behaving strangely, treat it as heatstroke and call 000. Do not wait to take a temperature and do not wait to see if they pick up.

Heat illness is the emergency Australians are most exposed to and least likely to name correctly. It also sits on a spectrum: heat exhaustion is unpleasant and recoverable, heatstroke can kill within hours, and one turns into the other if it is ignored. Knowing which one you are looking at decides whether you sit someone in the shade or dial 000.

Heat exhaustion or heatstroke?

The distinction is not about how hot the day is or how bad they feel. It is about the skin and the brain.

Heat exhaustion Heatstroke
Skin Cool, pale, clammy Red and hot, often dry
Sweating Still sweating, often heavily May have reduced or stopped
Temperature Normal or slightly raised Above 40°C
Mental state Weak, dizzy, headache, nausea — but making sense Confused, slurring, poor coordination, odd behaviour, may lose consciousness
Is it an emergency? Not usually, if they improve within about 30 minutes Always. Call 000.

One caution about the “dry skin” rule: it is a useful signal but not a requirement. Someone can still be sweating and be in heatstroke, particularly if they have been exerting themselves. Confusion outranks the skin.

Heat exhaustion: what to do

Signs include feeling very weak or dizzy, headache, nausea, thirst, heavy sweating, muscle cramps, and cool pale clammy skin.

  1. Get them out of the heat — indoors with air conditioning if possible, otherwise deep shade with moving air.
  2. Lie them down and loosen or remove excess clothing.
  3. Give cool fluids — cool water, a sports drink with electrolytes, or an oral rehydration solution. Avoid alcohol and caffeine.
  4. Cool the skin — a cool damp cloth or a light spray of water, with fanning.
  5. Watch them for about 30 minutes. They should steadily improve.

Call 000 if heat exhaustion comes with any of these: fainting or collapse, confusion, an inability to drink, vomiting that will not stop, seizures, or a temperature reaching 40°C. Also call if they are not clearly improving after about 30 minutes of cooling and fluids — that is heat exhaustion tipping into heatstroke.

Heatstroke: cool them down fast

Heatstroke is a medical emergency. The organs are being damaged by heat, and how quickly the temperature comes down is what determines the outcome. Do not wait for the ambulance to start cooling.

  1. Call Triple Zero (000) and say you think it is heatstroke.
  2. Move them into shade or air conditioning.
  3. Remove excess clothing.
  4. Wet their skin with cool water — a sponge, a wet cloth, a spray bottle or a hose.
  5. Fan them continuously. Moving air over wet skin is what actually removes heat — wetting alone does much less.
  6. Apply ice packs, or crushed ice in a damp towel, to the neck, groin and armpits. Cold packs to the cheeks, palms and soles help too.
  7. If they are conscious and someone can support them, cool water immersion is highly effective. Never leave a person unattended in water, and never immerse someone who is confused or drowsy.
  8. If they are conscious, give sips of cool fluid. Nothing by mouth if they are drowsy, confused or vomiting — they may choke.
  9. If they become unresponsive and are not breathing normally, start CPR and follow DRSABCD. If they are unresponsive but breathing normally, put them in the recovery position and keep cooling.

Keep cooling until paramedics take over or the person is clearly recovering. If they start shivering hard, ease off slightly — but do not stop.

Several common medications make heat illness more likely — and a confused patient cannot list them.

A MedibandPlus profile gives paramedics the medications, conditions, allergies and emergency contacts of the person in front of them, in seconds.

Store your conditions, medications and emergency contacts — explore MedibandPlus

Part of the Mediband family. Designed in Australia since 2004.

Who is most at risk

Heat illness is not evenly distributed, and some of the risk factors surprise people.

  • People taking medications that reduce sweating or cause dryness. This is the one most often missed — if you or someone you care for takes regular medication, it is worth asking a pharmacist whether heat is a factor.
  • People with chronic conditions that affect the body's ability to sweat or regulate temperature.
  • Babies, young children and older people.
  • People who are pregnant.
  • People with obesity or low fitness levels.
  • Anyone working or exercising hard in the heat, particularly if they are not used to it.

Children and cars

Never leave a child or a pet in a parked car, not even briefly with the windows down. The inside of a car heats far faster than the air outside, and small children cannot regulate their temperature the way adults do. If you see a child alone in a locked car, call 000 immediately.

Preventing heat illness

  • Drink water before you are thirsty — thirst lags behind fluid loss.
  • Shift hard work and exercise to early morning or evening.
  • Take breaks in the shade or air conditioning, and take them before you need them.
  • Wear loose, light-coloured clothing, a broad-brimmed hat and sunscreen.
  • Avoid alcohol and large amounts of caffeine in extreme heat.
  • Check on older neighbours and relatives during a heatwave — a hot house with no air conditioning is a genuine risk, and people living alone rarely call for help.
  • Give yourself time to acclimatise if you have arrived from a cooler climate or are returning to physical work after a break.

Related reading: what to say when you call an ambulance, the recovery position, and preparing for a natural disaster. If you take a medication that affects how your body handles heat, you can create your emergency profile before the next hot spell.

Heat illness FAQs

What is the difference between heat exhaustion and heatstroke?

In heat exhaustion the skin is cool, pale and clammy, the person is still sweating, their temperature is normal or only slightly raised, and they are weak and dizzy but still making sense. In heatstroke the skin is red and hot and often dry, sweating may have stopped, the body temperature is above 40 degrees Celsius, and the person is confused, slurring, uncoordinated or unconscious. Heat exhaustion is usually manageable with cooling and fluids; heatstroke is always an emergency.

When should you call an ambulance for heat illness?

Call 000 immediately for any suspected heatstroke, meaning confusion, slurred speech, poor coordination, odd behaviour, collapse or a temperature above 40 degrees. Also call if someone with heat exhaustion faints, becomes confused, cannot drink, keeps vomiting, has a seizure, or is not clearly improving after about 30 minutes of cooling and fluids.

How do you cool someone down with heatstroke?

Move them into shade or air conditioning, remove excess clothing, wet their skin with cool water and fan them continuously, because moving air over wet skin is what actually removes heat. Apply ice packs or crushed ice wrapped in a damp towel to the neck, groin and armpits, and cold packs to the cheeks, palms and soles. Cool water immersion works well if the person is conscious and someone can support them, but never leave anyone unattended in water. Keep cooling until help arrives.

How long should heat exhaustion take to improve?

About 30 minutes. Move the person somewhere cool, lie them down, give cool water or an electrolyte drink, and cool their skin. If they are steadily improving within roughly half an hour it was heat exhaustion. If they are not, or if they become confused or faint, call 000, because it is progressing to heatstroke.

Should you give someone with heatstroke water to drink?

Only if they are fully conscious and able to swallow safely, and then only sips of cool fluid. Give nothing by mouth if they are drowsy, confused or vomiting, because they may choke. Cooling the body is the priority, not fluids.

Can you get heatstroke without dry skin?

Yes. Dry, hot skin is a classic sign but it is not required, and someone who has been exerting themselves may still be sweating while their core temperature is dangerously high. Confusion, slurred speech, poor coordination or strange behaviour in someone who has been in the heat matters more than what their skin is doing.

Why do some medications make heat illness more likely?

Some medications reduce the body's ability to sweat or cause dryness, and sweating is how the body sheds heat. Some chronic conditions have the same effect. If you or someone you care for takes regular medication, ask a pharmacist or GP whether heat is a consideration, particularly before a heatwave.

Sources

Disclaimer: This article is general first aid information, not medical advice or a substitute for accredited first aid training. In an emergency, always call Triple Zero (000). For non-urgent health advice, call healthdirect on 1800 022 222 (NURSE-ON-CALL 1300 60 60 24 in Victoria, 13 HEALTH 13 43 25 84 in Queensland) or speak with your GP. If you are concerned that a medication may affect your tolerance of heat, speak to your pharmacist or GP rather than changing it yourself. MedibandPlus stores and provides access to a member’s own medical information; it does not assess, diagnose or treat any condition.

More first aid guides