Heatstroke in Thailand: Prevention, Symptoms & Emergency Treatment

The reality: Thailand's heat is real. Bangkok regularly hits 35-40°C in the hot season. Add humidity (feels like 45°C), UV index of 10+ (extreme), and a backpack on your shoulders — and your body goes into overdrive.

Every year, backpackers and tourists end up in Thai hospitals because they underestimated the heat. Most cases are preventable. This guide covers the difference between heat exhaustion (warning sign) and heatstroke (emergency), how to prevent both, and when to seek medical help.

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Heat Exhaustion vs Heatstroke: What's the Difference?

These are not the same thing. Heat exhaustion is your body's warning signal. Heatstroke is a medical emergency.

Heat Exhaustion (Warning Sign — Not an Emergency)

What it is: Your body is overheating but still trying to regulate itself through sweating.

Symptoms:

• Heavy, profuse sweating
• Weakness or fatigue
• Cold, pale, clammy skin (despite being in heat)
• Nausea or dizziness
• Headache
• Normal or slightly elevated body temperature

Timeline: Develops over hours, not minutes.

What to do:

1. Stop activity immediately
2. Move to shade or air conditioning
3. Drink water or electrolyte drink slowly (don't chug)
4. Cool your skin: wet cloth on neck, wrists, armpits
5. Rest lying down with legs elevated
6. Monitor yourself for next 30 minutes

Recovery: Usually improves within 30-60 minutes with cooling and hydration.

Heatstroke (EMERGENCY — Call for Help)

What it is: Your body's cooling system fails. Core temperature rises dangerously (above 40°C). Brain and organs start to malfunction.

Symptoms:

• Hot, dry skin (sweating has stopped — very bad sign)
• Confusion, disorientation, slurred speech
• Loss of consciousness or fainting
• Seizures
• No sweating despite extreme heat
• Body temperature above 40°C (if you can check it)
• Rapid, weak heartbeat
• Red, flushed skin

Timeline: Can develop rapidly (30 minutes to 2 hours) once it starts.

What to do — RIGHT NOW:

1. Call emergency services: 1669 (Tourist Police) or 1191 (Ambulance)
2. Cool aggressively: Ice packs on neck, armpits, groin. Cold water immersion if available.
3. Do not give oral fluids (person may not be conscious)
4. Lay person flat with legs slightly elevated
5. Stay with them until ambulance arrives
6. Tell medical staff the timeline (when did symptoms start?)

This is not a "ride it out" situation. Heatstroke can cause permanent brain damage or death. Get medical help immediately.

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Thailand's Climate Context

Temperature and Humidity

Bangkok and Central Thailand:

• January-February: 25-30°C (comfortable)
• March-May (hot season): 35-40°C, peaks at 42°C
• June-October (monsoon): 28-34°C, high humidity
• November-December: 25-32°C (returning to normal)

Chiang Mai:

• Similar pattern, slightly cooler than Bangkok (1-3°C difference)
• Burning season (March-April): smoke adds to heat perception

Islands (Phuket, Samui, Railay, Koh Tao):

• Consistently 28-35°C year-round
• Humidity: 70-90% (feels hotter than actual temperature)
• Sea breeze disguises how hot it is — you don't realize how much you're sweating

UV Index

Thailand's UV index is extreme almost year-round.

| UV Index | Risk | What Happens | |----------|------|--------------| | 10+ (Extreme) | Severe risk | Burns in 15 minutes, contributes to heat illness | | 8-10 (Very High) | High risk | Burns in 25 minutes | | 6-7 (High) | Moderate-high risk | Burns in 45 minutes |

In Thailand, you're usually in the 10+ range. Combined with heat, this accelerates heat illness.

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Heat Exhaustion Prevention: Timing, Clothing, Hydration, Sun Protection

Rule 1: Avoid Peak Heat Hours

Safe activity hours:

• 6:00 AM - 10:00 AM: Ideal for outdoor activities
• 3:00 PM - 6:00 PM: Acceptable, but sun still intense
• 10:00 AM - 3:00 PM: AVOID outdoor exposure

Why: The sun is highest and most intense during midday. UV index peaks around noon-1 PM.

Hot season (March-May) strategy: Plan temple visits, jungle hikes, and island hopping early. Rest at hostel/hotel during peak heat, explore malls and museums (free AC).

Rule 2: Wear the Right Clothing

Fabric choices:

• Linen: Breathes well, quick-drying, not great for hiking
• Bamboo fabric: Naturally moisture-wicking, soft, breathes like linen
• Merino wool: Yes, even in heat. Wicks moisture, regulates temperature, doesn't stink
• Synthetic athletic wear: Moisture-wicking if labeled as such

Avoid:

• Cotton (absorbs sweat, traps moisture)
• Tight clothing (restricts airflow)
• Dark colors (absorb heat)

Practical outfit:

• Light-colored, loose-fitting shirt
• Light-colored shorts or pants (long pants protect legs from sun burn)
• Wide-brimmed hat (protects face and neck)
• UV-rated sunglasses
• Moisture-wicking socks if hiking

Hostel rule: Most hostels in Thailand expect casual clothes. Light sundresses, shorts, and t-shirts are fine. Dress for heat, not formality.

Rule 3: Hydration Strategy

Minimum intake: 2-3 liters per day in normal conditions In extreme heat or activity: 3-5 liters per day With exercise: Add 500ml-1L per 30 minutes of activity

How much is a liter? Four 250ml bottles, or two 500ml bottles, or one 1L bottle.

What to drink:

• Water: Essential, but not enough on its own
• Electrolyte drinks: Pocari Sweat, coconut water, ORS (oral rehydration salts)
• Salty snacks: Chips, salted bread, or soup alongside water

Real schedule:

• Morning: 500ml upon waking
• Pre-activity (7-8 AM): 500ml
• During morning activity: 250ml every 15-20 minutes
• Rest period (11 AM - 3 PM): 500ml (even resting, you dehydrate)
• Afternoon activity (4-6 PM): 250ml every 15-20 minutes
• Evening: 500ml
• Total: 3-4 liters

Don't wait until thirsty. By the time you're thirsty, you're already dehydrated.

Rule 4: Sunscreen Discipline

SPF minimum: 50+ (in Thailand, use 50+, not 30) Type: Zinc oxide (physical/mineral) sunscreen recommended. It provides immediate UV blocking and doesn't absorb into skin.

Where to apply:

• Face (including ears and back of neck)
• Shoulders
• Tops of feet
• Any exposed skin

Reapplication: Every 2 hours, or immediately after swimming or heavy sweating.

Reality: Most backpackers reapply once mid-day and forget. Result: severe sunburn that adds to heat load.

Product recommendations:

• Available at: 7-Eleven, Boots (pharmacy), supermarkets
• Cost: 200-500 baht for a good one
• Local brands: Mistine, Sundown are cheap and work
• Familiar brands: La Roche-Posay, CeraVe available at Boots

Sun damage effect on heat: Severe sunburn increases core body temperature and impairs your body's ability to cool itself. A badly burned person is more susceptible to heatstroke.

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The Shade and Air Conditioning Strategy

Thailand's urban design is actually heat-friendly:

• 7-Eleven (open 24 hours, free AC)
• Shopping malls (free AC, food courts, bathrooms)
• Museums (AC, cultural value)
• Temples (often have cool interior spaces)
• Bookstores and cafes (cheap drinks + seating + AC)

Route planning during hot season:

• Map your path with 7-Eleven and malls as cooling stops
• Spend 15 minutes inside when you're getting warm
• Browse, grab a drink, reset core body temperature
• Continue

Bangkok example: Walking from BTS (Skytrain) Chong Nonsi to Lumphini Park

• Without stops: Brutal heat, high heat illness risk
• With 7-Eleven stops every 500m: Comfortable, safe, free AC breaks

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Specific Risk Zones

Bangkok (Central Thailand)

Risk level: Medium-High (urban, traffic adds heat)

• Concrete and cars radiate heat
• Hot season (March-May): Peak risk
• Busy sightseeing schedule + peak heat = dangerous combo

Prevention: Early temples (6-9 AM), lunch inside, museums/malls midday, evening night markets.

Chiang Mai

Risk level: Medium-High

• Cooler than Bangkok, but still hot
• Burning season (March-April): Smoke + heat = worse heat perception
• Hiking/trekking popular: Full sun exposure common

Prevention: Schedule treks for early morning (6-8 AM). Avoid peak season hiking (March-May).

Islands (Phuket, Samui, Railay, Koh Tao, Phangan)

Risk level: HIGH

• Beach sun is intense (reflecting off sand and water)
• Sea breeze feels cool but you're sweating heavily (can't see wet clothes)
• Island activities often midday (boat trips, diving, beach clubs)
• No shade on boats

Prevention:

• Reef shirt (UV-rated swimwear) on boats
• Sunscreen every 1-2 hours on water
• Dive early morning or late afternoon (safer, better visibility too)
• Beach club? Shade, water, electrolytes, sunscreen reapplication
• Not in sun 11 AM - 2 PM on first day of island arrival (acclimation period)

Burning Season Chiang Mai (March-April)

Risk level: VERY HIGH

• Smoke from agricultural burning reduces visibility
• Smoke makes air quality bad (respiratory irritation)
• Combination of heat + poor air quality = heightened heatstroke risk
• Visibility poor for outdoor activities

Prevention:

• N95 mask if air quality index (AQI) above 150
• Indoor activities prioritized
• Early morning outdoor activities (before smoke thickens)
• Check AQI (www.aqicn.org) before planning day

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Warning Signs: What to Watch For

Mild Heat-Related Symptoms (Monitor Closely)

• Fatigue more than usual
• Mild headache
• Thirst
• Slightly faster heartbeat

Action: Find shade, drink water, rest.

Escalating Heat Exhaustion (Serious — Take Action)

• Heavy sweating, but can't cool down
• Dizziness or lightheadedness
• Weakness in legs or body
• Nausea without vomiting
• Headache getting worse
• Skin feels cold despite being hot

Action: Stop activity immediately, move to AC, cool off, drink electrolytes, rest 30+ minutes.

Heatstroke (EMERGENCY — Call 1669 NOW)

• Confusion or slurred speech
• Loss of consciousness or fainting
• No sweating (body not trying to cool anymore)
• Skin is hot and red (not clammy)
• Rapid, weak pulse
• Seizure or tremors
• Temperature above 40°C if you can check

Action: Call 1669 immediately. Cool person aggressively while waiting for ambulance.

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First Aid for Heat Exhaustion

Timeline to improvement: 30 minutes

Step 1: Stop and Move

• Stop all activity immediately
• Move to shade or air conditioning (priority: AC is better)

Step 2: Cool the Person

• Remove excess clothing
• Apply cold water or wet cloths to: neck, wrists, armpits, groin
• Use ice packs if available (wrap in cloth, don't apply directly to skin)
• Spray bottle of water + fan = effective DIY cooling

Step 3: Hydrate

• Drink small sips of water (not huge gulps)
• Add electrolytes: coconut water, Pocari Sweat, or ORS sachet
• Sip slowly over 30 minutes
• Don't lie down and chug water (causes cramping)

Step 4: Rest

• Lie down with legs slightly elevated
• Stay in cool space
• Monitor for next 30-60 minutes

Step 5: Know When to Seek Help

• If person doesn't improve after 30 minutes of cooling
• If symptoms worsen (confusion, continued vomiting, fainting)
• If core body temperature won't come down
• Call: 1191 (Ambulance) or 1669 (Tourist Police)

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Recovery Timeline

Heat exhaustion: 1-2 hours with proper cooling and hydration.

After recovery:

• Don't jump back into activity immediately
• Rest remainder of day
• Increase fluids for next 24 hours
• Avoid intense heat for 24-48 hours

When to return to normal activity: When you feel normal and have eaten solid food without nausea.

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High-Risk Activities and How to Do Them Safely

Scuba Diving in Koh Tao or Railay

Why it's risky: Deep sun exposure (boat rides in direct sun), physical exertion underwater (generates heat), limited fluid intake between dives.

Safe approach:

• Early morning diving (6-8 AM start): Cooler water, less sun, better visibility
• Late afternoon diving (4-6 PM start): Sun lower, still good light
• Avoid midday dives
• Reef shirt + sunscreen mandatory on boat
• Reapply sunscreen between dives
• Drink water and electrolytes on surface interval (resting between dives)
• Tell dive operator you're concerned about heat (they'll keep an eye on you)

Full Moon Party at Koh Phangan (or Any Beach Party)

Why it's risky: All-night dancing in heat, alcohol dehydration, no structured breaks, peer pressure to keep partying.

Safe approach:

• Arrive well-hydrated (spend day before hydrating)
• Pace alcohol (alternate alcoholic drink with water)
• Wear light, reflective clothing
• Watch for signs in yourself and friends
• Take breaks in cooler areas (inside bar, shade structure)
• Have a designated person watching for heat illness symptoms
• Don't mix heavy alcohol + no sleep + heat

Jungle Trekking in Chiang Mai

Why it's risky: All-day sun exposure, physical exertion, limited water supplies, often in peak season (March-May).

Safe approach:

• Early start (6-8 AM departure): Cooler morning, avoids peak heat
• Carry 3+ liters of water minimum
• Wear lightweight long sleeves and pants (sun protection + insect protection)
• Take 15-minute shade breaks every hour
• Eat snacks with salt (jerky, salted peanuts)
• Avoid trekking in March-May hot season (go Nov-Feb instead)
• Use a local guide (they know safe pace and water stops)

Bangkok Temple Hopping (Walking Tours)

Why it's risky: Multiple temples = multiple transitions between hot streets and dark, cool temple interiors (body gets confused), long walking distances, tourist itineraries don't account for heat.

Safe approach:

• Go early (6-9 AM) or late (4-6 PM)
• Wear sunscreen before leaving hostel
• Carry water (refillable bottle)
• Don't try to visit more than 3-4 temples per day
• Take long breaks inside temples (sit, cool off, enjoy the air)
• Plan route near convenience stores for AC breaks
• Wear a hat

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Special Populations at Higher Risk

Older Travelers (55+)

Why vulnerable: Sweat response diminishes with age, thirst sensation weakens, medications can impair heat regulation.

Extra precautions:

• Hydrate before you're thirsty
• Consider electrolyte supplementation (ORS daily)
• Schedule activities before 10 AM only
• Check blood pressure medications (some affect heat tolerance)
• Take more frequent rest breaks

Travelers with Certain Medications

Heat sensitivity increased by:

• Antihistamines (allergy meds)
• Some blood pressure medications
• Diuretics (water pills)
• Stimulants

Action: Check with doctor before trip. Medication + tropical heat sometimes requires adjusted dosing or timing.

Overweight Travelers

Why vulnerable: Extra mass = harder to cool, higher metabolic heat production.

Approach: Not discouraging — just plan more conservatively. Lower intensity, more breaks, earlier activity times.

Travelers with Previous Heat Illness

Risk factor: Once you've had heat exhaustion, you're more susceptible again (sometimes for weeks).

Recovery: Wait 2-3 weeks before intense heat exposure. Use all prevention strategies religiously.

Pregnant Travelers

Why vulnerable: Increased core body temperature baseline, higher metabolic rate, dehydration risk increases.

Precautions: Hydrate aggressively, avoid peak heat hours entirely, monthly checkups with obstetrician before trip, alert hostel staff to pregnancy (they can offer cooling aid).

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When to Seek Medical Help

See a Doctor Within 24 Hours

• Mild heat exhaustion that doesn't improve
• Any vomiting related to heat
• Heat exhaustion in someone who's pregnant
• Heat illness in someone with pre-existing conditions

Call Emergency Services (1191 or 1669) Immediately

• Loss of consciousness
• Confusion or slurred speech
• Seizures
• Temperature above 39.5°C with severe symptoms
• No improvement after 30 minutes of cooling
• Any signs of heatstroke

Hospitals in Major Tourist Cities

• Bangkok: Bumrungrad International Hospital (English-speaking, accustomed to tourist cases)
• Chiang Mai: Bangkok Hospital Chiang Mai
• Phuket: Phuket International Hospital
• Samui: Samui International Hospital

All are accustomed to heat-related illnesses in tourists.

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Quick Reference: Your Heat Safety Checklist

Before Your Day:

• [ ] Weather check (temperature, UV index)
• [ ] Activity planned for 6-10 AM or 3-6 PM? (Avoid 11 AM - 2 PM)
• [ ] Sunscreen applied (SPF 50+)
• [ ] Water bottle filled (2L minimum)
• [ ] Electrolyte drink or salty snacks packed
• [ ] Hat and sunglasses ready
• [ ] Light-colored clothing on
• [ ] Route planned with shade/AC stops

During Activity:

• [ ] Drinking water every 15-20 minutes (not waiting until thirsty)
• [ ] Checking urine color (dark yellow = drink more)
• [ ] Sunscreen reapplied every 2 hours
• [ ] Monitoring for early symptoms (headache, dizziness, weakness)
• [ ] Taking breaks in shade/AC every 60 minutes

After Activity:

• [ ] Cool off in shade (avoid jumping in cold water — too sudden)
• [ ] Drink electrolyte drink (not just water)
• [ ] Monitor for delayed symptoms (can take hours to fully develop)
• [ ] No intense activity for rest of day

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The Bottom Line

Thailand's heat is manageable. People live and thrive here year-round. Backpackers successfully visit in peak season every year.

The difference between safe and unsafe is planning ahead: arriving hydrated, avoiding peak heat hours, wearing protective gear, reapplying sunscreen, and recognizing early warning signs.

Heat exhaustion is a teaching moment. Heatstroke is an emergency.

Stay hydrated, time your activities, and you'll enjoy Thailand's incredible heat instead of suffering from it.