Cycling in the heat
Heat is not something you get fitter at. It is a limit you plan around, and the planning is mostly done before you leave the house.
General information, not medical advice. Heat illness can be serious. If you have a heart condition, take medication that affects hydration or temperature regulation, or are pregnant, take advice from a doctor who knows your situation.
Riders in hot countries work this out quickly, and riders visiting from cooler ones frequently do not. The mistake is treating heat as something to push through, the way you might push through a headwind. It is not the same kind of problem.
The single biggest lever is the clock
Nothing else you do comes close to simply riding earlier. Setting off at first light in summer gives you the coolest air of the day, the emptiest roads, and several hours before heat becomes the deciding factor.
| When | What it is like |
|---|---|
| First light to mid-morning | The good window – cool, quiet, and comfortable |
| Late morning | Warming quickly; fine for a short ride, hard work for a long one |
| Midday to mid-afternoon | Avoid. This is where people get into trouble |
| Early evening | Cooling but the ground still radiates heat; watch the light |
If your only free time is the middle of the day, shorten the ride rather than pretending the heat is not there.
Water: carry two, plan the rest
You cannot carry a hot day of water. Two litres on the bike is a sensible working load, and everything beyond that comes from refilling as you go.
Plan refills before you leave
Know roughly where the springs, cafes and shops are on your route. On rural roads these are the difference between a good ride and a bad one.
Fill whenever you pass water
Not when you are low. If you pass a spring with half-full bottles, fill them anyway. The next one may be much further.
Drink to a schedule, not to thirst
In heat, thirst arrives late. Small sips at regular intervals absorb better than a bottle drunk at once.
Add electrolytes on long rides
Heavy sweating loses salt as well as water. Plain water alone over many hours leaves you flat.
Carry a little cash
A shop that will fill your bottles is worth more than any piece of equipment when you are two hours from home.
Do not drink enormous quantities of plain water on a long hot ride. Replacing heavy sweat loss with water alone can dilute the sodium in your blood, which is dangerous. It is uncommon, but more is not automatically better – water plus electrolytes is.
Warning signs worth stopping for
Heat problems build gradually and then arrive quickly. The point of knowing the signs is to stop while stopping is still easy.
- Your effort feels much harder than the speed you are producing
- A headache building through the ride
- Feeling cold, or goosebumps, while riding in heat
- You have stopped sweating despite the temperature
- Dizziness, nausea, or confusion about simple things like which way home is
The last two are serious. Stop, get into shade, drink, and cool your skin with water. Do not attempt to ride home to prove a point. If confusion or nausea does not clear quickly, get help.
Clothing and sun
- Light colours and loose weave beat bare skin - covering up in the sun is cooler than burning
- Sunscreen on everything exposed, reapplied on long rides
- A cap under the helmet shades your face and holds water if you pour some on it
- Sunglasses, because glare is genuinely tiring over hours
- Pour water on your head and forearms at refills - evaporative cooling works and costs nothing
The bike in the heat
- Tyre pressure rises as the tyre heats up - inflate at the lower end of your usual range on very hot days
- Do not leave the bike in direct sun for hours if you can avoid it, especially the tyres and saddle
- Bottles in direct sun become undrinkably warm; an insulated bottle is a genuine upgrade here
- Salt from dried sweat corrodes - rinse the bike occasionally, as covered in the cleaning guide
Altitude helps
If you have hills nearby, they are a heat strategy as well as a training one. Air cools with altitude, so climbing out of a hot plain often means riding into genuinely more comfortable conditions – one reason the climb into the Middle Atlas is a summer favourite.
Remember that you have to come back down into the heat, usually later in the day when it is hotter. Plan the return as carefully as the climb.
Three rules for hot-weather riding
Leave at first light
The clock does more for you than any equipment. In summer, an early start is the whole strategy.
Fill at every opportunity
Two litres on the bike, topped up whenever you pass water. Plan the route around refills.
Stop at the early signs
Headache, unusual effort, feeling cold in the heat. Stopping early is easy; stopping late may not be your choice.
Questions about riding in hot weather
There is no single number – humidity, wind, effort and how used to it you are all matter. The practical rule is to move the ride to the early morning rather than pick a temperature threshold.
More than the usual 500-750ml, and to a schedule rather than to thirst. The precise figure varies enormously between people; plan refills so that running out is not possible.
On rides over about 90 minutes in real heat, yes – they help you retain what you drink and replace the salt lost in sweat.
Cover up with light, loose clothing. Bare skin in strong sun heats faster and burns, and burnt skin cools less effectively.
Stop in shade, drink, wet your skin, and wait. Riding on while feeling unwell in heat is how a manageable situation becomes a serious one.
You do adapt to heat over a couple of weeks, and it is real. It does not remove the limit – it raises it slightly.
Related guides
Three more that pair naturally with this one.
Cycling in Ramadan
The two windows that work while fasting – before iftar, or after Tarawih.
Cycling in Morocco
Roads, drivers, water, heat and shops – what riding here is actually like.
Fuel matters more in the heat
The food and drink guide covers what to eat and drink by ride length, and how to avoid the bonk.