Heat exhaustion in Thailand: signs, what to do and when it’s an emergency
Heat exhaustion in Thailand usually gets better within 30 minutes if you get somewhere cool, drink and rest. Heatstroke is different: hot skin that stops sweating, confusion or collapse is a medical emergency, so call 1669 straight away. This guide shows you how to tell them apart and how to stay safe in the heat on Koh Phi Phi.
The short version
Heat exhaustion in five points
- Spot it early: headache, dizziness, nausea, heavy sweating, cramps and feeling very thirsty after time in the heat.
- Cool down now: shade or air conditioning, loose clothing off, cool water on the skin and a fan.
- Drink: water plus oral rehydration salts or a sports drink, sipped steadily.
- Give it 30 minutes: if the person isn’t clearly better, treat it as heatstroke.
- Heatstroke is an emergency: hot skin without sweating, confusion, a seizure or collapse means call 1669 and keep cooling while you wait.
Why Thailand’s heat catches visitors out
Southern Thailand is hot all year, but it’s the humidity that surprises most visitors. Your body cools itself by sweating, and sweat only cools you when it evaporates. In thick, humid air it can’t evaporate quickly, so you keep sweating, lose water and salt, and still don’t cool down. The hottest months are March to May, just before the rainy season, but a still, sunny afternoon on Phi Phi can be draining at any time of year.
On Koh Phi Phi the risky moments are easy to predict:
- The viewpoint hike in the middle of the day: steep steps, full sun and little breeze.
- Boat trips to Maya Bay and the snorkelling spots, with hours on a deck in the sun.
- Long Beach and Loh Dalum at low tide, when there’s little shade on the sand.
- The day after a big night, when you’re already dehydrated before you step outside.
- Your first few days, before your body has adjusted to the climate, especially straight off a long flight.
Heat exhaustion vs heatstroke: how to tell the difference
Heat exhaustion is your body struggling to keep cool. Heatstroke is when it has stopped coping and your temperature keeps rising, which can damage the brain and organs. This table, based on NHS guidance, shows the difference:
| Heat exhaustion | Heatstroke | |
|---|---|---|
| Skin | Sweating heavily, pale and clammy | Hot, may look red, and may stop sweating |
| Temperature | High | Very high |
| Mind | Tired, irritable, dizzy | Confused, restless, poorly coordinated, may have a seizure or pass out |
| Other signs | Headache, nausea or vomiting, cramps, very thirsty | Fast breathing and fast heartbeat |
| After 30 min of cooling | Feeling better | Still unwell |
| What to do | Cool down, drink, rest | Call 1669 and keep cooling |
“Sunstroke” is an older name for heatstroke caused by the sun. It is just as serious, so treat it the same way.
What to do for heat exhaustion
Act as soon as you notice the signs, in yourself or a friend. The NHS advice is four simple steps:
- Move somewhere cool. On Phi Phi that might be your air-conditioned room, a café, or the nearest 7-Eleven, which are all air-conditioned.
- Remove unnecessary clothing, such as a shirt over a swimsuit, a hat that traps heat or tight shoes.
- Drink plenty of water. A sports drink or oral rehydration salts mixed with water also replace the salt lost in sweat.
- Cool the skin. Spray or sponge with cool water and fan, or take a cool shower. Cold packs or a bag of ice wrapped in a cloth under the armpits or on the neck help too.
Stay with the person. They should start to cool down and feel better within about 30 minutes. If they don’t, or they get worse at any point, treat it as heatstroke.
Heatstroke is an emergency, not a drip
Call 1669 (Thailand emergency medical services) straight away if someone is still unwell after 30 minutes of cooling, or has a very high temperature, hot skin that isn’t sweating, fast breathing or a fast heartbeat, confusion, a seizure or loses consciousness. Your hotel reception can help you call and guide the ambulance to you. While you wait, keep cooling them: a cool, wet sheet, fanning and sponging with cold water. If they pass out, put them in the recovery position and check their breathing. Please don’t wait for a hotel IV drip: heatstroke needs a hospital, and on Phi Phi that can mean a transfer to the mainland.
Dehydration medicine in Thailand: what to buy
You don’t need a prescription for the basics. Every pharmacy in Tonsai and every 7-Eleven on the island sells what you need to rehydrate after too much heat:
- Oral rehydration salts (ORS): small sachets of powder you mix with clean drinking water. In Thai they’re called glua rae (เกลือแร่), which means “mineral salts”, so you can show the word to the pharmacist. Follow the instructions on the packet for how much water to use.
- Sports and electrolyte drinks from the 7-Eleven fridge. Fine for most adults, though many are sugary.
- Bottled water: buy the big bottles and keep one in your room. Don’t drink tap water on Phi Phi.
- Coconut water is refreshing and has some potassium, but less salt than you lose in sweat, so it doesn’t replace ORS.
Avoid alcohol and lots of strong coffee until you feel normal again. If you’re on regular medication, especially for blood pressure, the heart or diabetes, ask a pharmacist or doctor whether the heat affects it.
How to avoid heat exhaustion on Koh Phi Phi
Most heat illness on holiday is avoidable with a few simple habits:
- Avoid the strongest sun between 11am and 3pm. Do the viewpoint at sunrise or late afternoon, and plan beach time for the morning.
- Drink before you’re thirsty and carry water everywhere, including on boat trips. Pale yellow pee means you’re drinking enough.
- Wear light, loose clothing, a hat and sunglasses, and use plenty of sunscreen. Sunburn makes it harder for your body to cool down.
- Ease in. Take the first two or three days gently while your body adjusts, particularly after a long-haul flight.
- Go easy on alcohol, especially buckets in the afternoon sun, and drink water between drinks.
- Keep your room cool: air conditioning or a fan, curtains closed during the day.
Who is most at risk?
Anyone can get heat exhaustion, but the NHS highlights young children, older people and people with long-term conditions such as diabetes or heart problems. On Phi Phi we would add travellers who are already dehydrated: after food poisoning, a hangover or a long dive day. Some medicines also affect how your body handles heat, so check with your doctor before you travel if you take regular medication.
Children can go downhill quickly. Keep them in the shade, offer drinks often and get medical help early if a baby or young child is floppy, unusually sleepy or not having wet nappies.
Can an IV drip help with heat exhaustion?
An IV drip is never the first step. Cooling down and drinking come first, and most people recover fully with those alone. Where a drip can help is afterwards: when you feel washed out, keep getting headaches, or feel too sick to drink enough to catch up. Our hydration IV drip on Phi Phi replaces fluids and salts in about 30–45 minutes, in your room, with a nurse checking your blood pressure first.
If you have any of the heatstroke signs above, a drip is not the answer: call 1669. Our guide to medical help on Koh Phi Phi explains where the clinics are and how hospital transfers to the mainland work.
Heat FAQ
Heat exhaustion in Thailand: your questions
How long does heat exhaustion last?
With cooling, rest and fluids, most people feel better within 30 minutes and are back to normal within a day. You may feel tired and headachy for the rest of the day, so take it easy and keep drinking.
What is the hottest time of year in Thailand?
March to May is the hot season in Thailand, before the monsoon rains arrive. Koh Phi Phi is hot and humid all year, so heat illness can happen in any month.
Is it heat exhaustion or a hangover?
They feel alike, and they often happen together: alcohol dehydrates you before you go out in the sun. If you feel dizzy, sick and headachy in the heat, cool down and drink first. Confusion, hot dry skin or collapse is never just a hangover. Call 1669.
Can I swim when I have heat exhaustion?
No. Dizziness, cramps and nausea are dangerous in the water. Cool down in the shade or a cool shower, and wait until you feel completely normal.
Do I need to see a doctor after heat exhaustion?
Usually not, if you feel better within 30 minutes and stay well. See a doctor if symptoms come back, you can’t keep fluids down, or you have a heart or kidney condition.
Keep reading
Staying well in the heat on Phi Phi
See IV drip vs drinking water to find out when fluids by mouth are enough, or read our guide to diving and dehydration if you’re spending your days on a dive boat. For an itchy red rash in the heat, see heat rash in Thailand.
Sources: NHS: Heat exhaustion and heatstroke · WHO: Heat and health · NHS: Dehydration. Last updated October 2026.
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