The wind lies to you. At 60 km/h the airflow over a moving motorbike evaporates sweat as fast as you produce it, so you feel cool and dry while losing a great deal of fluid, and you get burnt without ever feeling hot. Riders routinely arrive at their destination badly sunburnt, well behind on fluid, and — the part that matters — with their concentration already degraded, having noticed none of it happening.
Both problems are trivially preventable and both are worse in Thailand than most visitors expect, because the sun is close to overhead, the humidity is high enough that sweat does not cool you efficiently once you stop moving, and the riding season for tourists coincides with the hottest months. The fix is unglamorous: cover up, drink far more than feels necessary, and stop more often than you planned to.
- What hides the heatAirflow on a moving bike
- First thing to goConcentration, before thirst
- Worst hoursRoughly 11:00–15:00
- Medical emergency1669, for suspected heat stroke
Why sunburn on a bike is different
Three things make riding a uniquely efficient way to burn.
First, the cooling wind removes the feedback that normally tells you your skin is getting hot, so you will not feel the burn developing. Second, Thailand sits close to the equator, so the sun is high and UV strong for much of the day, all year — cloud cuts the sensation of heat far more than it cuts the UV. Third, riders present a very consistent set of surfaces to the sun for hours: the backs of the hands, the forearms, the tops of the thighs, the back of the neck between helmet and collar, and on an open-face helmet the nose and lower face.
The result is the classic rider's burn — scarlet forearms and hands, a stripe across the neck, white patches where a watch and a glove cuff were. Severe sunburn also genuinely impairs your ability to concentrate and to regulate temperature the following day.
- Sun cream on before you set off, not when you arrive. High factor, and reapplied at every stop — sweat and wind strip it faster than swimming does.
- Do not miss the back of the hands, the back of the neck, the ears and the tops of the feet. These are the four areas riders reliably forget.
- Cover beats cream. A thin long-sleeved shirt outperforms any sun cream and does not need reapplying. Light colours, loose weave.
- A visor or sunglasses. Squinting into tropical glare for three hours is fatiguing on its own, and grit in the eye at speed is a crash risk. See choosing a helmet for why a clear visor matters as much as a tinted one here.
- Lips. Everyone forgets them and they are miserable when burnt.
The visible skin under a mesh jacket still burns. Mesh passes UV as happily as it passes air. If you are riding in mesh over bare arms, you are not covered — a thin base layer under the jacket solves both this and the abrasion problem. Protective riding clothing in a hot climate covers the layering.
Dehydration: the one that affects your riding
Sunburn ruins your evening. Dehydration is the one that puts you in a ditch.
Fluid loss impairs concentration, reaction time and judgement before it produces any dramatic symptom, and thirst is a late signal rather than an early one — by the time you are properly thirsty you are already behind. On a bike the losses are high, because you are sweating continuously into moving air and never see the evidence. A rider who would notice a soaked shirt in a car arrives dry, and concludes they were fine.
The practical signs to watch for in yourself, in roughly the order they appear:
| Sign | What it means | What to do |
|---|---|---|
| Dark yellow urine, or not needing to go | The most reliable early indicator | Drink now, and keep drinking |
| Headache, tiredness, irritability | Already meaningfully dehydrated | Stop, get in the shade, drink, wait |
| Losing focus, missing turnings, sloppy gear changes | Your riding is affected | Stop riding for at least half an hour |
| Muscle cramps | Fluid and salt loss | Stop, shade, fluids with salt in them |
| Dizziness, nausea, clammy skin, weakness | Heat exhaustion | Stop immediately, cool down, rehydrate; get help if it does not improve within about half an hour |
| Confusion, no sweating, very hot skin, collapse | Possible heat stroke | Medical emergency — call 1669 |
Heat stroke is a medical emergency, not a bad afternoon. Someone who becomes confused, stops sweating, has very hot skin or collapses needs an ambulance on 1669 and active cooling in the meantime — into shade, clothing loosened, water on the skin. Do not put them back on a bike and do not wait to see whether they improve.
What to drink
Water is the baseline and it is everywhere — every 7-Eleven, petrol station and roadside stall. On a long, hot day plain water is not quite the whole answer, because you lose salt as well as fluid; oral rehydration salts cost very little in any Thai pharmacy, and convenience-shop electrolyte drinks do a reasonable job. Roadside coconut water is a perfectly good option and a pleasant reason to stop.
What not to do: substitute coffee or energy drinks for water, or drink alcohol at lunch. Beyond the legal problem — Thailand's lower 0.02% blood-alcohol limit applies to anyone riding without the right licence category — alcohol accelerates dehydration on precisely the day you can least afford it.
Planning a hot day's riding
The heat is not evenly distributed through the day, and the single most effective change is when you ride rather than how you dress.
- Start early. Between about 06:30 and 10:00 Thailand is pleasant, the light is good and the roads are quieter. A 07:00 departure changes the character of a long day completely.
- Take the middle of the day off. Roughly 11:00 to 15:00 is when the sun is highest and the heat is worst. A long lunch in the shade is not lost time — it is the thing that lets you ride well at four o'clock.
- Stop every hour, whether you feel you need to or not. Fifteen minutes, shade, a drink. On a bike you have no idea what your fluid balance is doing, so operate on a schedule rather than on how you feel.
- Plan the stops. Petrol stations on Thai highways are excellent for this — shade, a shop, a toilet and usually somewhere to sit. Service areas and rest stops on Thai highways covers what to expect.
- Carry water on the bike. Under the seat or in a tank bag. The stretch where you decide you can push on to the next town is the stretch where having a bottle with you matters.
- Shorten the day. The distance you would cover comfortably at home is too far here. Fatigue on long drives and rides covers how far to plan.
Wet the shirt. A base layer or shirt soaked at a rest stop cools you dramatically for the next half hour of riding, because the airflow that was hiding your sweat now works for you instead. It costs nothing, it dries within the hour, and long-distance riders in hot countries have done it forever.
Where it bites hardest in Thailand
Two situations catch visitors out specifically.
The northern mountain loops. Roads like the Mae Hong Son loop combine high concentration demand with long gaps between stops, and heat plus fatigue on hairpin bends is a poor combination. Build the stops into the plan before you start.
Island days. Short distances lull people into treating a whole day of riding as nothing. Six half-hour rides between beaches in full sun, with swimming in between, adds up to a badly burnt and dehydrated rider by five o'clock — and the ride back over the hill in the dark is the one that goes wrong.
One counter-intuitive point: the rainy season does not solve this. Humidity is higher, sweat evaporates less efficiently, and the sun between downpours is as strong as ever. If anything, riders drink less on a cloudy day because they do not feel the heat. Riding a motorbike in tropical rain covers the rest of what changes.
Frequently asked questions
How much should I drink on a day's riding in Thailand?
More than feels necessary, and on a schedule rather than by thirst — thirst is a late signal. The reliable check is urine colour: pale means you are keeping up, dark yellow means you are behind. On a full day in the heat, add oral rehydration salts or an electrolyte drink rather than relying on water alone.
Can I get sunburnt through cloud in Thailand?
Yes, comfortably. Cloud cuts the sensation of heat far more than it cuts UV, which is exactly why overcast days catch people out. The airflow on a bike removes the other warning signal, so a cloudy riding day is one of the easier ways to get badly burnt.
Does a mesh jacket protect me from the sun?
Not reliably — mesh passes UV. A thin light-coloured base layer underneath does, and it also helps you stay cool by moving sweat into the airflow. Bare arms under a mesh jacket burn.
What is the difference between heat exhaustion and heat stroke?
Broadly: heat exhaustion is dizziness, nausea, weakness and clammy skin, and it usually improves with shade, rest and fluids. Heat stroke involves confusion, very hot skin, often no sweating, and possible collapse — that is a medical emergency and needs an ambulance on 1669. If you are unsure which one you are looking at, treat it as the serious one.
Do I need salt tablets?
Oral rehydration salts from a pharmacy, or a normal electrolyte drink, are a better and safer answer than salt tablets for the amount of riding a visitor does. They cost very little and are sold everywhere.
Is this a problem on a bicycle too?
Worse, because you are generating heat as well as absorbing it, and you have less airflow. How to cycle in Thailand's heat and humidity covers the version of this problem that applies to cyclists.