You have spent months logging early morning miles, hitting long runs on tired legs, and fine-tuning your race-day plan. The last thing you want is for rising temperatures to undo all that hard work. Yet overheating remains one of the most common and most preventable reasons runners drop out, slow dramatically, or end up in the medical tent.
Here is the thing: UK marathons are no longer a guaranteed cool-weather experience. Spring events like the London Marathon regularly see temperatures climbing into the low twenties, and summer trail and road races can push further still. Even modest warmth, combined with high humidity, can create conditions your body finds genuinely challenging.
This guide covers everything you need to know about preventing overheating in a marathon, from the science of how your body handles heat to the practical steps you can take before, during, and after your race. You will find advice on heat acclimation, hydration strategy, cooling techniques, clothing choices, pacing adjustments, and what to do in an emergency. Work through each section, apply what fits your situation, and you will be far better prepared to race safely when the temperature climbs.
Understanding Overheating in Marathon Running
The Science of Body Temperature Regulation During a Marathon
Running a marathon generates a remarkable amount of metabolic heat. For every unit of energy your muscles convert into movement, around 75 percent is released as heat rather than mechanical output. Your body works hard to keep core body temperature within a safe range, and sweating is the primary mechanism it uses to do that.
When sweat reaches the surface of your skin, evaporation carries heat away from your body. This process is highly effective under the right conditions, but it depends on two things: enough fluid to produce sweat, and enough airflow and low enough humidity to allow evaporation to happen efficiently.
Your resting core body temperature sits around 37°C. During a marathon, it will typically rise to somewhere between 39°C and 40°C, which is a normal physiological response to sustained exercise. The danger zone begins when core body temperature edges above 40°C. At that point, the risk of serious heat illness increases dramatically, and your body's systems begin to struggle.
One of the key physical mechanisms behind this is the competition for blood flow. When you overheat, your body diverts blood towards the skin to help with cooling, pulling it away from your working muscles. That diversion slows you down and, crucially, reduces the efficiency of heat dissipation at the very moment you most need it to be effective.
Understanding this basic physiology helps you appreciate why every strategy in this guide matters. Cooling, hydration, pacing, and clothing choices all feed into the same outcome: keeping your core temperature in a manageable range for the full 42 kilometres.
Heat-Related Illnesses Runners Must Know
Not all overheating is equal. There is a spectrum of heat-related illness that moves from uncomfortable to life-threatening, and knowing where you sit on that spectrum could save your life or someone else's.
Heat stress is the mildest form. Your body is under thermal strain, working harder than usual to regulate temperature, but it is still coping. You might feel unusually tired or flushed, but your cognitive function and coordination remain intact.
Heat exhaustion is more serious. Symptoms include heavy sweating, weakness, nausea, headache, and a racing pulse. Your body is struggling to keep up, but you are still conscious and relatively coherent. Heat exhaustion requires you to stop, cool down, and rehydrate immediately.
Heat stroke is a medical emergency. It occurs when core temperature exceeds 40°C alongside central nervous system dysfunction, including confusion, disorientation, loss of coordination, and in serious cases, loss of consciousness. Heat stroke can cause organ damage, including kidney and liver failure, and can be fatal without immediate treatment. Critically, it can occur even in moderate UK temperatures if humidity is high or a runner is underprepared.
The progression from heat stress to heat stroke can happen faster than you expect, especially in the latter stages of a marathon when your reserves are depleted. Do not wait for advanced symptoms before taking action. Heat illness caught early is manageable; heat illness left untreated is dangerous.
Warning Signs and Symptoms of Overheating
Knowing what to look for in yourself and in fellow runners around you is one of the most valuable things you can do in a hot marathon.
Early warning signs to watch for:
- Excessive sweating that feels beyond what the effort justifies
- Dizziness or lightheadedness
- Muscle cramps, particularly in the legs or abdomen
- Headache
- Nausea
- Feeling noticeably hotter than the effort level seems to warrant
Advanced symptoms that demand immediate action:
- Confusion or difficulty thinking clearly
- Loss of coordination or stumbling
- Cessation of sweating despite the heat (a serious red flag)
- Visual disturbances
- Shivering or goose bumps on a hot day
- Feeling cold or clammy despite warm conditions
The tricky part is distinguishing between normal race fatigue and dangerous overheating. Normal fatigue during a marathon involves aching legs, general tiredness, and a sense of effort. Overheating involves your cognitive function deteriorating. If you are struggling to remember what kilometre you are on, cannot recall your name, or are weaving across the road, these warning signs are not about tired legs. They are about your brain.
If you experience confusion, shivering in the heat, or cessation of sweating, stop running immediately. Walk or sit in the shade and get to the nearest aid station or wave down a marshal. Do not try to push through these symptoms.
The Role of Environmental Factors
Temperature alone does not tell the full story. The heat index, which combines ambient temperature with humidity, gives you a much more accurate picture of how your body will actually experience race-day conditions.
Here is why humidity matters so much: your body cools itself through evaporation of sweat. When the air around you is already saturated with moisture, sweat cannot evaporate efficiently. You can be dripping wet and still not cooling down effectively. High humidity essentially defeats your body's primary cooling system.
Direct sun exposure adds another layer of heat exposure through radiant heat, warming your skin and raising core body temperature beyond what air temperature alone would suggest. A temperature of 18°C in full sunshine with 80 percent humidity is a very different challenge to 18°C in the shade with a breeze.
Research consistently shows that marathon performance declines measurably above 15°C, with each additional degree Celsius adding roughly one to two minutes to overall finish time across the field. The optimal marathon temperature sits between 7°C and 15°C. Beyond that range, everyone slows down.
Before your race, check the weather forecast carefully. Look at three figures together: temperature, humidity percentage, and the heat index. If the forecast shows high humidity combined with temperatures above 15°C, adjust your entire race-day strategy accordingly. Some races will modify start times or even cancel events in extreme weather conditions, so check official communications in the days before your race.
Pre-Race Preparation and Heat Acclimation Strategies
Heat Acclimation Training
Heat acclimation is the process of gradually adapting your body to exercise in warm conditions through repeated heat exposure, typically over 10 to 14 consecutive days. It is one of the most powerful tools available to marathon runners preparing for a warm-weather race, yet it is often overlooked.
Research shows that maintained core temperature above 38.5°C for at least 60 minutes, repeated over 10 to 14 days, creates the most effective adaptation, producing a 6 to 8 percent improvement in time trial performance within 10 days.
The physiological adaptations are impressive. Within three to five days, plasma volume expands by around 4 percent, boosting blood volume and improving your cardiovascular efficiency in heat. Over four weeks of controlled heat acclimation, research documents a 0.4°C reduction in resting core temperature during submaximal exercise, a 21 percent increase in sweat rate, and a significant reduction in electrolyte losses through sweat, including sodium, which drops from around 60 mmol/L to 10 mmol/L.
Your sweat glands become more efficient, starting to cool you earlier in a run. Your heart rate at the same exercise intensity drops. Your body becomes better at tolerating the thermal strain of racing in heat. These adaptations also build heat tolerance in a way that meaningfully reduces your risk of heat illness on race day.
The CORE 2 thermal sensor is an invaluable tool for athletes aiming to optimize their performance through precise heat management. By monitoring real-time thermal data, athletes can safely engage in heat training, which is proven to enhance haemoglobin mass and VO2 max, leading to improved endurance and overall fitness. On race day, the CORE 2 allows users to track their thermal status, enabling them to make informed decisions about cooling strategies and pacing to maintain peak performance.
Practical methods for heat acclimation:
- Running at moderate intensity (around 50 percent of VO2max) in warm conditions
- Adding extra layers during training runs to artificially raise body temperature
- Passive approaches, such as hot water immersion after training sessions
- Using a sauna after cool-weather runs if warm outdoor conditions are not available
Start your heat acclimation programme roughly two to three weeks before your target race, and do not try to compress it into the final three or four days. Your body needs time to adapt.
Pre-Cooling Techniques Before the Race
Pre-cooling is about lowering your core body temperature before the gun goes off, creating a larger heat-storage buffer that delays the point at which you reach dangerous temperature thresholds. Think of it as building yourself a head start in the thermal race.
Research shows pre-cooling can improve performance by 5.7 to 16 percent in hot conditions, and 80 percent of athletes at the 2019 World Athletics Championships in Doha used pre-cooling techniques before their events.
The three main pre-cooling approaches:
Ice slurry ingestion. Drinking a crushed-ice drink 20 to 30 minutes before the start is practical, effective, and easy to organise on race morning. Ice slurry lowers core body temperature from the inside out, providing a meaningful buffer before you begin generating metabolic heat.
Cold water immersion and ice bath protocols. A brief ice bath or cold water immersion in the hours before racing can lower core temperature. The logistics on a race morning can be tricky, but if you have access to a bathtub, a cold soak for 10 to 15 minutes is worthwhile.
Cooling vests. Wearing an ice vest for 10 to 20 minutes during your warm-up can lower core body temperature by up to 2.6°C and improve performance by up to 16 percent in hot conditions. They are a favourite tool among elite athletes and are worth hiring or borrowing for a hot race.
There is an important caveat to keep in mind: pre-cooling benefits diminish significantly after 20 to 25 minutes of running. For a full marathon, which lasts three to five or more hours, pre-cooling is just one piece of the puzzle. You must combine it with mid-race cooling strategies to sustain the benefit.
Monitoring Weather Conditions and Race Timing
Start checking the weather forecast seriously about five days out from your race. In the days leading up to it, look at temperature, humidity, and heat index together rather than focusing on temperature alone.
The ideal marathon start time is early morning, ideally before 8 or 9am, to take advantage of lower temperatures and reduced solar radiation before the day heats up. If your race has a choice of wave start times and a warm day is forecast, push for the earliest available slot.
Use the forecast to shape your race-day strategy well before you arrive at the start line. If the heat index is projected to be significantly higher than you trained in, plan for a slower pace and build in more cooling stops. Some race organisers in the UK and internationally may modify start times or cancel events when weather conditions pose genuine danger, so keep an eye on official communications.
Give yourself personal permission to withdraw from a race if conditions are extreme and you have any doubts about your preparation or health. Finishing a marathon next month is better than ending up in hospital this one. Safety is always the priority.
Hydration and Fluid Management Strategies
Understanding Dehydration and Its Impact on Overheating
Dehydration and overheating are deeply connected. When you lose fluid through sweating, your blood becomes thicker and your total blood volume drops. This makes it harder for your heart to pump blood to both your working muscles and your skin for cooling. The result is that your core body temperature rises faster and your cooling mechanisms become less effective at exactly the moment you need them most.
Losing just 2 percent of body weight through sweat can noticeably impair performance, while losses above 3 to 4 percent significantly increase the risk of heat illness. For a 70kg runner, 2 percent body weight loss means just 1.4 litres of sweat, which can happen in less than an hour of hard running in warm conditions.
Marathon runners are particularly vulnerable to dehydration-induced overheating because they are sweating heavily and continuously for anywhere from three to six or more hours. Even a small, steady deficit compounds into a serious problem by the second half of the race. Getting your hydration strategy right from the outset is not optional in warm conditions; it is essential.
Optimal Fluid Intake Planning
Personalising your fluid intake starts with knowing your sweat rate. A simple way to calculate this is to weigh yourself before and after a training run in similar conditions to your race. One kilogram of body weight loss equals approximately one litre of sweat lost. This gives you a reliable starting point for how much you need to replace.
For most marathon runners in hot conditions, the recommended fluid intake is 400 to 800ml per hour, taken as roughly 150 to 250ml every 15 to 20 minutes. If you are a heavier sweater or conditions are particularly hot and humid, lean towards the upper end of that range.
On race morning, aim to pre-hydrate with 500 to 1,000ml of fluid containing electrolytes about two hours before the start. This tops up your fluid stores without leaving you with a desperate need for the toilet at the start line.
A vital warning: over-hydration is a real and underappreciated danger. Hyponatraemia, which occurs when excess water dilutes sodium levels in the blood, can be life-threatening and is more common in marathon runners than many realise. Do not drink to a rigid schedule if you are not thirsty and not sweating heavily. Drink to thirst, guided by your sweat rate calculations and adjusted for conditions.
Use water stops and aid stations strategically. In hot conditions, plan to drink at every station rather than skipping any. Having a plan means you will not forget in the fog of racing.
The Role of Electrolytes and Sodium
Water alone is not enough. Sweat contains significant amounts of minerals, most importantly sodium, and replacing fluids without replacing electrolytes creates its own serious problems.
Sodium is the most critical electrolyte for marathon runners in hot conditions. It helps your body retain fluid, maintains blood volume, and prevents the dangerous electrolyte imbalance that can lead to hyponatraemia. Sweat typically contains between 300 and 1,000mg of sodium per litre, and when you are running hard in the heat, sodium loss accelerates substantially.
Research recommends 600 to 1,000mg of sodium per hour during a hot marathon, adjusted upward for heavy sweaters. If you regularly see a white residue on your skin or kit after a long run, you are a salty sweater and you are likely losing more than average.
The comparison between plain water, electrolyte drinks, and sports drinks matters here:
|
Option |
Pros |
Cons |
|---|---|---|
|
Plain water |
Readily available, no GI risk |
Does not replace sodium or other electrolytes; risk of diluting sodium levels over marathon distance |
|
Sports drinks |
Combines sodium, carbohydrate, and fluid for good absorption |
Can be sugary; individual GI tolerance varies |
|
Electrolyte drinks (low or zero carb) |
Replaces minerals without high sugar |
Does not provide energy for the race |
For most runners, the best approach is to use electrolyte drinks or sports drinks at water stops throughout the race rather than relying on plain water alone. If the race only provides water, carry electrolyte tablets or capsules in your kit and take them at regular intervals. One encouraging note: heat-acclimated runners lose less sodium in sweat, giving yet another reason to do those adaptation sessions before race day.
Practical Hydration Execution During the Race
Knowing the theory is one thing. Executing it smoothly in the middle of a marathon is another.
At aid stations, slow your pace slightly to drink properly rather than spilling most of the cup on your shoes. Pinching the top of the cup into a spout makes drinking while moving much easier. Grab water to drink and, where possible, a second cup to pour over your head and neck.
Think about whether to carry a personal hydration system (a handheld bottle or a running vest) or rely entirely on race water stops. In a race with water stops every five kilometres, you should be fine without a personal system if your fluid intake needs are moderate. If you sweat heavily or the stops are further apart than ideal, carrying your own supply gives you peace of mind and more control.
Signs of dehydration mid-race: increasing thirst, darker urine before the start, dizziness, and a rising heart rate out of proportion to pace.
Signs of overhydration: a bloated, sloshing feeling in your stomach, swollen fingers, and feeling nauseous despite drinking at a normal pace.
Adjust your fluid intake dynamically. If conditions get hotter than forecast or your pace is higher than expected, increase your intake. If you feel waterlogged, ease off and let your body catch up.
Race-Day Cooling Techniques and Body Cooling Methods
Active Cooling Strategies During the Race
Mid-race cooling is where you make the biggest difference to your core body temperature during a marathon, and the best part is that most of what you need is available at every aid station.
Research shows that pouring cold water over your head and neck can help runners complete a 10km effort in 30°C conditions approximately 27 seconds faster. That might not sound like much in isolation, but the cooling effect compounds over the course of a full marathon. Do this at every aid station from the halfway point onwards and it adds up meaningfully.
Applying ice to your pulse points, including your wrists, neck, and inner elbows, provides rapid localised cooling by chilling blood close to the surface as it circulates. Using wet sponges provided at water stops to dampen your skin promotes evaporative cooling as you run, giving you a similar benefit to sweating more efficiently.
These external cooling methods work by drawing heat from the blood flowing near the skin's surface, which then circulates back to cool your core. It is not just about comfort; it is a genuine physiological intervention.
Body cooling during the race is particularly valuable. Research shows during-race cooling improves performance by around 9.9 percent, which is actually more impactful than pre-cooling alone for marathon-length efforts. Do not skip aid stations just to save a few seconds. The time you spend cooling is paid back in the kilometres that follow.
Cooling Vests and Wearable Cooling Technology
Cooling vests contain either ice packs or phase-change materials that absorb heat from your torso over time. They are proven to lower core body temperature by up to 2.6°C in controlled research settings and are a popular tool among serious runners.
The practical reality for use during a marathon is more complicated, though. Cooling vests add weight to your body. The cooling effect fades as the ice melts, typically within 20 to 30 minutes of running. Resupplying mid-race is almost impossible unless you have a dedicated support crew stationed at a specific point on the course.
For most runners, cooling vests are better treated as a pre-race body cooling tool: wear one during your warm-up for 10 to 20 minutes before the gun goes off, then hand it to a support person or check it into gear storage. If you can access one through your club or hire it for the day, it is genuinely worthwhile for that pre-start period.
Lighter alternatives that work better during the race itself include ice-filled neck wraps and wet bandanas. These are easy to carry, can be refreshed at aid stations, and target effective cooling zones without the weight penalty.
Ice Slurry and Cold Fluid Ingestion During the Race
You have already seen how ice slurry works as a pre-cooling tool. It can also be used during the race to lower core body temperature from the inside out, complementing the external cooling methods you are applying at aid stations.
Research confirms that ice slurry consumption provides significant benefit for endurance performance in the heat, and the internal cooling effect works differently to skin cooling, offering a meaningful additional benefit when combined with external methods.
The practical challenge is availability. Most standard marathon aid stations in the UK do not routinely provide ice slurry. Larger events and international races are more likely to offer ice. Where ice is available, combine a small amount with your water for a cold drink rather than a standard-temperature one.
If the race allows it and you want to take this approach seriously, carrying a small insulated flask with crushed ice is an option worth considering in longer, hotter events. Combining internal cooling through ice slurry with external cooling through water dousing and sponges gives you the most comprehensive temperature management available.
Seeking Shade Along the Running Route
Running in shade is a straightforward but often underestimated way to reduce heat exposure during a marathon. Direct sunlight adds radiant heat that bypasses your normal cooling mechanisms entirely, warming your skin from the outside and increasing the thermal load your body has to manage.
Before race day, study the running route and identify which sections are tree-lined or shaded and which are exposed. On race morning, position yourself on the shady side of the road wherever the course allows it. Over 42 kilometres, even small reductions in solar radiation add up.
Race organisers can help runners significantly by routing courses through shaded areas, though in many city marathons this is not always possible. In races where you have freedom to choose your position across the road, make shade-seeking a conscious habit rather than an afterthought. It requires almost no extra effort and asks nothing of your legs.
Running Attire and Sun Protection
Choosing the Right Clothing for Hot Marathons
What you wear has a direct effect on your ability to stay cool. The right running attire creates the conditions for sweat evaporation to work effectively. The wrong choices trap heat and moisture, working against your body's cooling system.
Key principles for hot-weather marathon clothing:
- Fabric: Choose lightweight, moisture-wicking technical fabrics. Polyester and nylon blends designed specifically for running are far superior to cotton, which absorbs sweat, becomes heavy, and impairs evaporation. Once a cotton shirt is soaked, it stops doing anything useful.
- Colour: Light-coloured clothing reflects solar radiation rather than absorbing it. A white or pale-coloured vest will keep you meaningfully cooler than a dark shirt under direct sun.
- Fit: Both loose and fitted options can work. Loose clothing allows airflow across the skin, while well-fitted moisture-wicking fabrics spread sweat over a larger surface area for more efficient evaporation. Avoid very tight, non-breathable fabrics that restrict airflow entirely.
- UPF rating: Consider UPF-rated running attire if you want sun protection built into your clothing, particularly for exposed areas like your shoulders and arms. UPF 50+ rated fabrics block up to 98 percent of UV rays without requiring sunscreen on covered skin.
Avoid wearing anything new on race day that has not been tested in training. Heat amplifies rubbing and chafing, and discovering that your new shorts cause blisters at kilometre 25 is an avoidable problem.
Hats and Head Protection
Your head is one of the primary areas of heat gain in direct sunlight. Wearing a hat or visor reduces direct sun exposure significantly and can meaningfully lower the thermal load on your body over the course of a long race.
Choose a breathable, light-coloured hat made from mesh or ventilated fabric. The goal is sun protection without trapping heat against your head. A thick, heavy baseball cap in a dark colour defeats the purpose entirely.
The visor versus full hat debate is a genuine one. Visors allow heat to escape freely from the top of your head while still shading your face, which makes them often preferable in very hot conditions where head heat dissipation matters. A full hat with good ventilation and a light colour is a reasonable choice when cloud cover limits direct sunlight, as it also protects from rain.
If you are running in particularly intense sun, a hat with a wider brim or a neck flap provides additional protection for your ears and the back of your neck, which are areas that burn easily and are easy to forget when applying sunscreen.
Sunscreen Application and Sun Protection
Position sunscreen as what it actually is: a safety measure, not an afterthought. Sunburn damages the skin's ability to produce sweat effectively, directly impairing your body's cooling system at the cellular level. Running 42 kilometres with sunburned skin is not just painful; it is physiologically counterproductive.
Use SPF 30 or higher, applied 20 to 30 minutes before your warm-up begins so it has time to bond with your skin before you start sweating. Choose a sweat-resistant formula designed for sport. Standard sunscreen products designed for beach use often wash off quickly in heavy sweating conditions and leave you unprotected by halfway.
Research confirms that sunscreen does not adversely affect thermoregulation, so there is no performance trade-off here. It is pure benefit.
Commonly missed areas:
- Backs of the ears
- Back of the neck
- Tops of the shoulders
- The V of exposed skin at the neckline
- Backs of the legs if wearing shorts
Apply generously and do not rush the process. A few minutes of careful sunscreen application at the start protects you for the entire race.
Pacing Strategy and Race Execution in Heat
Adjusting Pace for Hot and Humid Conditions
This is perhaps the most important single decision you will make on a hot race day. Maintaining your cool-weather target pace in heat forces your body to produce more metabolic heat than it can possibly dissipate. The result is a progressive and dangerous rise in core body temperature that compounds with every kilometre.
The science on pace adjustment is clear: research suggests slowing by approximately 20 to 30 seconds per mile for every 5 degrees Fahrenheit (approximately 2.8°C) above 60°F (15°C). As a starting point, a 2.5 to 3 percent reduction in goal pace covers many realistic warm-weather scenarios in the UK. For a runner targeting 4:00, that means starting at around 4:06 to 4:07 pace.
When conditions are significantly hotter than you trained in, recalibrate your goals entirely. Switch from pace-based targets to effort-based running. Your heart rate or perceived exertion becomes your guide, not your GPS watch. This is not giving up on your race; it is racing intelligently.
Data shows that each 1°C above the optimal 7 to 15°C range adds roughly one to two minutes to overall marathon time across the field. On a day that is 5°C above your training conditions, planning for 5 to 10 minutes slower than goal pace is realistic, not pessimistic.
Start conservatively. A slower first half in heat buys you a crucial heat margin. Runners who go out at target pace in warm conditions rarely negative split; they blow up spectacularly in the second half instead. A conservative start that leaves you feeling controlled through 30 kilometres is far more race-day satisfaction than a fast first half followed by a death march.
Strategic Use of Aid Stations
In normal conditions, experienced runners often skip aid stations to save time. In hot conditions, that logic reverses completely. Aid stations become your most important tactical tool.
Plan to stop at every single aid station when it is hot. No exceptions. The time you spend there is an investment in the second half of your race.
At each stop, try to:
- Grab at least one cup of water or electrolyte drink to consume
- Grab a second cup to pour over your head, neck, and wrists
- Use any sponges or ice that are available
- Spend five seconds checking in with yourself: are you thinking clearly? Is your heart rate higher than expected for this pace? Are you aware of any symptoms of overheating?
Brief communication with volunteers can also be useful. Ask what cooling supplies are available before you reach the end of the table. If ice is available, do not leave it behind. Use aid stations as brief recovery checkpoints, not just fluid stops.
As precautions go, having this framework planned before race day means you will execute it even when you are tired and your decision-making is reduced. Build the habit in training by practising at stations on long run routes.
Mental Strategies for Managing Heat During a Marathon
The psychological challenge of racing in heat is real and underappreciated. It is genuinely difficult to let go of a target time you have worked towards for months. But ego-driven pacing in hot conditions dramatically increases your overheating risk, and the consequences can be severe.
Give yourself explicit permission to slow down before you reach the start line. Build a strategy with multiple plans:
- Plan A: Conditions are cooler than expected; race close to target pace.
- Plan B: Warm but manageable; add 5 to 8 percent to goal time, run by effort.
- Plan C: Hot and humid; focus on finishing safely, cooling at every station, and walking if needed.
The most important mental shift is framing safety as smart racing rather than failure. A runner who pulls out or slows significantly in dangerous heat and recovers fully can race again in four to eight weeks. A runner who pushes through heat stroke symptoms may be dealing with consequences for months.
Build these decisions into your race plan before the morning of the event. When you are at kilometre 28, tired, hot, and emotionally invested, you want to be following a pre-made decision framework rather than making fresh judgements on depleted cognitive function.
Safety Measures, Race Organisation, and Emergency Protocols
Pre-Race Safety Precautions for Runners
Before any hot-weather marathon, take a few minutes to address some important precautions that many runners overlook.
If you have any history of heat illness, a cardiovascular condition, or other health concerns that might affect your response to heat, speak to your GP before racing. Heat is a genuine physiological stressor, and underlying conditions can make you more vulnerable.
Inform a running partner, friend at the finish, or race official about your personal heat sensitivity before the race. If you are someone who struggles in the heat, that is useful information for people who might be watching you.
Review the specific race's heat management plan and emergency response protocols ahead of time. A well-organised event will have these published in runner communications or on its website. Know what provisions are in place before you toe the line.
Familiarise yourself with the running route in terms of medical tent locations. Knowing exactly where medical support is at kilometres 10, 20, and 30 means you can make faster decisions if you need help. This preparation takes ten minutes but could matter enormously on the day.
Race Organisation Responsibilities in Preventing Overheating
When you are choosing a race to enter, it is worth knowing what good heat management looks like from an organisational perspective. Well-run events take weather conditions seriously and put safety measures in place well before the start.
Responsible race directors will:
- Monitor weather forecast data in the days before the event and be willing to modify start times or cancel if conditions are extreme
- Increase the number and frequency of water stops in hot conditions (every three to four kilometres rather than every five)
- Provide ice, cold water, electrolyte drinks, and sponges at aid stations, not just plain water
- Deploy medical personnel specifically trained in recognising and treating heat illness
- Communicate clearly with runners about conditions and any adjustments to the event
When entering a spring or summer marathon in the UK, look for evidence that the organiser has a documented heat management plan. Events that take weather conditions seriously and plan accordingly are worth choosing over those that do not. Your safety is partly in their hands as well as your own.
Emergency Response to Overheating During a Marathon
Despite all precautions, heat stroke and severe heat exhaustion do occasionally occur in marathons. Knowing what the correct emergency response looks like could save a fellow runner's life.
The fundamental principle is: cool first, transport second. Rushing a heat stroke victim straight to hospital without beginning cooling wastes critical time. On-site cooling is the priority.
Cold water immersion is the gold-standard emergency treatment for heat stroke. The protocol involves immersing the runner neck-deep in water at approximately 10°C and monitoring until their rectal temperature drops below 38.6°C. This typically takes around 30 minutes.
At the Brighton Marathon, cold water immersion was used to successfully revive a runner with a core temperature of 41.9°C who was drifting in and out of consciousness. The intervention worked, and the runner recovered. This case illustrates both how extreme heat stroke can become in seemingly moderate UK conditions and how effective rapid body cooling can be.
Immediate steps if you see a runner collapse or show signs of heat stroke:
- Call for medical assistance immediately and loudly
- Move the runner to shade
- Remove excess clothing
- Begin cooling with any available cold water or ice while waiting for the medical team
- Do not leave the runner alone
After experiencing significant overheating during a race, even if you recover quickly on the day, do not rush back into hard training. Post-race monitoring and a gradual return to running are important. Your body has been through a serious physiological event, and it needs time to fully recover before you stress it again.
Conclusion
Preventing overheating in a marathon comes down to three things: preparation, smart execution, and knowing when to adjust your plans. None of this requires expensive equipment or elite-level physiology. It requires knowledge, planning, and the willingness to act on what you know even when race-day adrenaline is pushing you in a different direction.
The key pillars to carry forward:
- Heat acclimation in the weeks before your race, building the physiological adaptations that make you more resilient
- Pre-cooling before the start to build your heat-storage buffer
- Hydration with electrolytes, planned around your personal sweat rate and executed at every aid station
- Mid-race cooling techniques using water, ice, and sponges at every available opportunity
- Appropriate clothing and sunscreen to reduce radiant heat gain and protect your skin's cooling ability
- Conservative, effort-based pacing that accounts for the real physiological cost of running in heat
- A safety-first mindset that gives you permission to slow down or stop before symptoms become dangerous
Practise these strategies in training, particularly on your longer runs in warmer weather. Nothing should be new on race day. The runner who arrives prepared, paces sensibly, and manages their cooling and hydration throughout the race is the one who enjoys the finish line, whatever the temperature.
With the right precautions in place, you can race safely, smartly, and with confidence, even when the British weather decides not to cooperate.