Heat Exhaustion or Heatstroke? The Signs That Turn a Hot Day Into a 000 Call

Someone you love is lying on the couch after an afternoon out in the heat. They look flushed, they say they feel awful, and you’re torn between letting them sleep it off and picking up the phone. It’s a horrible spot to be in, and if you’re there right now, it’s okay to feel unsure. Here’s the reassuring part: there is a clear line between feeling terrible in the heat and needing an ambulance, and healthdirect, the government-funded health information service, draws it plainly on its heatstroke page (last reviewed in May 2026). The short helper below walks you through that line using the signs in front of you. It isn’t a diagnosis, and if you’re ever in doubt, call 000.

Three stages, from uncomfortable to emergency

It can help to think of heat illness as a ladder rather than a single thing. Healthdirect describes three rungs.

Heat stress comes first. You’re thirsty, tired and sweaty. It’s uncomfortable, and it’s the mildest of the three.

Heat exhaustion is the next step up. Healthdirect describes someone who feels very weak and dizzy, may have a headache or nausea, and has clammy skin. It feels dreadful and it needs proper care, and the care is rest, fluids and cooling.

Heatstroke is the top rung, and it’s a different situation altogether. This is when the body can’t cool itself any more. The temperature rises to a dangerous level, the person may stop sweating, and they can become confused or lose consciousness. Heatstroke is a medical emergency, and it’s a 000 call.

NSW Health draws the same line in its own guidance on heat-related illness. Heatstroke needs emergency care straight away. Heat exhaustion needs first aid, and then medical advice if the person isn’t improving. Two services, one message, which is a comfort in itself: you’re not choosing between conflicting opinions.

If you’re looking at someone and wondering which rung they’re on, you’re asking exactly the right question, and the sections below are there to help you answer it.

The signs of heatstroke

Healthdirect describes heatstroke as a body temperature of 40 degrees C or higher, together with changes in the way the brain and nerves are working. You won’t always have a thermometer to hand, so the other signs matter just as much:

• red, hot or dry skin
• reduced sweating, or no sweating at all
• nausea, vomiting or diarrhoea
• poor coordination
• strange or aggressive behaviour
• loss of consciousness

Healthdirect also lists warning signs to take seriously: being unable to carry on with usual activities, weakness, dizziness, confusion or seizures.

It’s easy to talk yourself out of that last group. Someone who is muddled, cranky or not quite making sense after a hot day might simply seem tired. But a change in how a person is thinking or behaving is one of the things that separates heatstroke from heat exhaustion, so it deserves your attention.

If one manageable step helps here, it’s this: when someone has been in the heat and seems “not themselves”, treat that as a sign, not a mood.

What to do for heat exhaustion

If the person is weak, dizzy and clammy but still alert and making sense, healthdirect’s advice is gentle and practical:

1. Move them somewhere cool.
2. Give them cool water, an electrolyte drink or an oral rehydration solution to sip.
3. Avoid caffeine and alcohol.
4. Take off any heavy clothing.
5. Cool them down with a cool shower or cold packs.
6. Use a fan or air conditioning.
7. Stay with them.

That last one matters more than it might seem. Heat exhaustion that isn’t settling needs a second look, and the person who feels unwell may not be the best judge of how they’re going.

Healthdirect is clear about when it’s time to call 000 instead: if the person feels faint, is confused, can’t drink, has a seizure, or has a temperature of 40 degrees C. If any of those happen, you’re no longer managing heat exhaustion at home.

The small step for this section is simply to stay close. Sit with them while they cool down, and keep an eye on whether they’re getting better or not.

What to do for heatstroke while the ambulance comes

If you think it might be heatstroke, call 000 first. Then you can start helping while you wait. If the person isn’t breathing, begin CPR.

Healthdirect’s steps for cooling someone with heatstroke are:

• move them into the shade
• loosen their clothing
• cool them from the neck down in cold water for 15 minutes, or wet them with a shower or a hose
• put ice packs on the groin, armpits, cheeks, palms and soles of the feet
• keep them damp with a moist cloth or a spray of water
• fan them continuously
• give cool drinks only if they’re fully conscious and able to swallow

There’s one thing healthdirect asks you not to do, and it might surprise you. Don’t give paracetamol, aspirin or ibuprofen. It’s a natural instinct to reach for something that brings a fever down, but healthdirect explains that these medicines won’t lower the body temperature in heatstroke.

It’s frightening to wait for an ambulance with someone this unwell. Keeping your hands busy with the cooling steps is the most useful thing you can do, and it’s okay if your hands are shaking while you do it.

Two hot afternoons, as examples

Sometimes it’s easier to see the line when it’s drawn through a real-feeling moment. These two afternoons are illustrations, not real cases, and they’re here to show how healthdirect’s signs fit together.

The first afternoon. Your teenager comes in from helping at a weekend sports carnival. They’re sweaty and clammy, they say they feel dizzy and a bit sick, and they flop onto the couch. When you ask what day it is and what they had for lunch, they answer straight away, a little grumpily. You move them to the coolest room, put a fan on them, hand them cool water to sip and help them out of their heavy shirt. Over the next while they sit up, drink more and start to look like themselves again. That’s the picture of heat exhaustion improving with rest and cooling, and staying with them until they’re properly better is the right next step.

The second afternoon. An older relative has spent the day in a hot house. When you arrive, their skin is red and hot to touch, and you notice they don’t seem to be sweating even though the room is stifling. They’re muddled, repeating themselves, and snap at you in a way that isn’t like them. Here you don’t wait to see whether rest helps. Confusion, strange behaviour and skin that’s hot with little or no sweating are heatstroke signs, so you call 000, then start cooling them while the ambulance comes.

The difference between the two isn’t how dreadful the person looks. It’s whether their thinking and behaviour have changed, and whether they’re getting better with care.

Who is most at risk

Anyone can become unwell in the heat, but healthdirect names the people most at risk:

• young children
• people over 65
• people who are pregnant or breastfeeding
• people who work outdoors
• people experiencing homelessness
• people with a chronic illness
• people taking medicines that affect how the body responds to heat

You might recognise yourself, or someone close to you, on that list. That isn’t cause for alarm. It’s a reason to plan a little earlier and to check in a little more often when the weather turns.

If someone in your own home is on the list, it can help to talk about the hot days before they arrive: where the coolest room is, who will check on whom, and what you’ll do if someone starts to feel unwell. A plan made calmly in spring is far easier to follow than one made up on a 40-degree afternoon.

Here’s one step that makes a real difference to someone else: during a heatwave, check on an older neighbour. A knock on the door or a quick call is often all it takes.

A few questions people ask

Can heat exhaustion turn into heatstroke? Healthdirect describes heat illness in stages, and its advice is to call 000 if someone with heat exhaustion feels faint, becomes confused, can’t drink, has a seizure or reaches 40 degrees C. So keep watching, even once you’ve started cooling them.

Why does it matter whether their skin is clammy or dry? Clammy skin is one of the signs healthdirect lists for heat exhaustion. Red, hot or dry skin, and sweating that has eased off or stopped, are on its list for heatstroke.

Before the first heatwave

It’s much easier to get ready for hot weather on a mild spring day than in the middle of a 40-degree week. Healthdirect’s prevention advice is straightforward:

• wear a hat and light, loose clothing
• drink water before you feel thirsty
• on hot days, set the air conditioning below 26 degrees
• if you don’t have air conditioning at home, spend time in cool public spaces
• avoid being out in the hottest hours of the day
• never leave a child in a parked car

Heatwave warnings come from the Bureau of Meteorology and from state health departments, so it’s worth knowing where to look for them before summer arrives. On a hot day there may be more than one warning to read, too. The fire danger rating is another one worth reading on a hot day.

If a beach day is part of your plan for beating the heat, it helps to know how to spot a rip current before anyone goes in. And while you’re putting the summer kit together, it’s a good moment to check whether your sunscreen has expired, so it’s ready for the first hot weekend.

One small step to finish: before the first heatwave, decide where you would go to cool off if the power went out or the air conditioning couldn’t keep up. Having that answer ready can take some of the worry out of a hot week.

Cool first, then decide

When someone is unwell in the heat, you don’t have to work everything out at once. Start cooling them. Move them somewhere shaded, loosen their clothes, and get water on their skin. While you’re doing that, look for the signs that change everything: confusion, strange behaviour, a seizure, loss of consciousness, skin that’s red, hot and dry, or sweating that has stopped. Any of those means calling 000.

If the person is alert, drinking and improving with rest somewhere cool, it’s likely heat exhaustion, and healthdirect’s steps above will help them recover. Stay with them, and call 000 if they feel faint, can’t drink or become confused.

You’re allowed to call for help even if you’re not sure. That’s what the number is for.

Sources: Heatstroke, healthdirect (https://www.healthdirect.gov.au/heatstroke); Heat-related illness: signs, symptoms and first aid, NSW Health (https://www.health.nsw.gov.au/environment/beattheheat/Pages/heat-related-illness.aspx)