Top tips for running in the heat

Whether you’re training for an autumn marathon, want to exercise on a trip to the tropics, or are returning to running in the summer, you are likely to find yourself running in heat conditions. Going running in the heat can be very rewarding and enjoyable. But it’s also important to be aware of some of the safety issues that can arise when exercising in high temperatures.

Before you start to run in the heat, it’s helpful to know a little more about what happens to your body when training in hot weather. In this guide you’ll also find out about the potential benefits and dangers of running in the heat, and we’ve provided tips for safe warm weather workouts too. 

What happens to your body when you run in the heat?

To function correctly, our bodies need to maintain a stable core temperature of about 37C. So, when you work out in hot weather, your body has several methods for cooling you down to prevent overheating:

• Sweat: As soon as you begin running in the heat, you’ll begin sweating much more than usual. Sweat comes out onto the surface of our skin. As it evaporates, it cools us down. 

• Blood flows to the skin: If you’ve ever touched your skin while exercising in the heat, you might have noticed it feels warmer than usual. This is because when you start sweating, your body pumps more blood to the skin - which is then cooled by evaporation when you sweat.

• Heart works harder: Your heart needs to work harder than usual when running in the heat, partly because it needs to pump more blood to the skin. This means that it becomes harder to run at higher speeds and over longer durations. 

• Changes to your metabolism: Some parts of our metabolism (the chemical reactions that keep us alive and help us get energy from food) speed up when running in heat. Researchers have found that people who exercise in heat use more muscle glycogen (an energy store) and have greater levels of lactate in their blood (a byproduct of exercise). 

Are there any benefits of running in heat?

Running in the heat can provide several benefits - not only in terms of enjoyment, but also for its effects on your body. That said, it’s important to be aware of certain dangers of running in the heat too - we’ll discuss them in more detail below. 

Some of the key benefits of running in heat include:

• Could improve performance

There are several studies which have found that running in the heat can lead to physical changes in athletes - and these could improve their performance. 

For example, one study with professional rowers who spent five days getting acclimatised to high temperatures improved their rowing speed and saw a variety of physiological changes. This suggests that being exposed to heat may have helped their fitness. 

Other research has found hot weather training can increase blood plasma volume (the amount of red and white blood cells in your blood) and make your heart more effective at delivering oxygen to muscles. 

• Running in the heat may burn more calories

When you run in the heat, your body temperature rises, and that means you use more energy cooling yourself down. That means you may burn more calories when working out in hot weather. However, as explained in our article on burning calories when running, the increase in calorie usage is fairly small. 

• Can be more enjoyable

Many people simply prefer running in warm weather. You don’t have to worry about the cold, wind and rain, and you can simply enjoy being out in the warm sunshine. 

• Vitamin D: Exposure to sunlight helps your body produce Vitamin D, which helps support many of your body’s processes.

What are the dangers of running in the heat?

Running in the heat can pose certain health risks, and it’s important to be aware of them before you start exercising in hot weather. By taking some simple precautions, you can really reduce your chances of being affected by any of these issues. 

• Dehydration

Perhaps the biggest danger of running in the heat comes from dehydration. You will sweat much more when running in high temperatures, and this can cause dehydration. Mild dehydration can cause confusion, and affect your blood pressure and body temperature. Severe dehydration can cause serious damage to your brain and kidneys.

• Heat exhaustion 

Heat exhaustion happens when you lose more water and salts than you take in. It can cause weakness, dizziness and a rapid pulse. 

• Heat stroke

Heat stroke is a medical emergency which happens when your body’s cooling mechanisms fail and your core body temperature rises to dangerous levels. Symptoms include confusion, lack of sweating and seizures. 

• Electrolyte imbalance leading to cramps and other issues

Your body uses electrolytes like sodium (salt) for many different processes in the body, but sodium levels drop when you sweat too much. In mild cases, this can cause cramps, but in more severe cases can lead to seizures and other issues. 

• Heart health problems

Research shows that working out in the heat makes your heart work harder. For people who have pre-existing heart conditions, exercising in the heat could increase their risk of cardiac events. 

• Poorer performance

For people who aren’t acclimatised to warm weather, there’s a lot of evidence that running in heat leads to worse overall performance. For example, one long term study of marathons and weather conditions found that hot temperatures are closely linked to higher numbers of non-finishers in races. 

Spotting signs of heat exhaustion 

The NHS heat exhaustion and heatstroke page lists numerous symptoms of heat exhaustion, including:

• Tiredness

• Feeling sick

• Headache

• Dizziness

• Excessive sweating

• People with lighter toned skin may look visibly paler than usual

• Cramps

• High temperature

• Being very thirsty

The NHS page has more advice on treating heat exhaustion and information on when to call emergency services. 

7 tips for running in heat safely and enjoyably

If you plan to start running in the heat, it’s helpful to do some planning and preparation to make sure you avoid possible risks such as dehydration or heat exhaustion - and can experience all the benefits of warm weather training. Here are our top tips for running in the heat.  

1. Acclimatise to the weather

Before you start running in the heat, it’s a good idea to give your body time to acclimatise to the warm weather before doing intensive exercise. An article in the British Medical Journal recommends that people taking part in events in hot weather should spend at least 1-2 weeks getting used to the hot conditions while doing light exercise. This gives your body time to adapt before taking part in more intense activities such as a marathon. 

2. A proper hydration plan

According to research, exercise in the heat can increase the average person’s sweat rate by 10-20%. Studies also indicate that some athletes can lose up to 2.5 litres of sweat in an hour. This is why it’s really important to have a hydration plan when running in heat. 

• First, prehydrate by drinking more water than usual in the hours before you work out. 

• Next, drink one final glass of water before you begin the run itself. 

• Carry a bottle of water, a bottle belt or a hydration vest and take regular sips throughout your run. 

• After completing your run, consume an energy drink that contains electrolytes. 

3. Wear the right running attire

When running in the heat, it’s very important to wear suitable running clothing. Running gear for the summer is designed to do several important things:

• Wick sweat: Running clothing uses technical fabrics which draw moisture from your skin to the outside surface of the clothing where it can evaporate, helping to cool you down. If you don’t wear sweat wicking clothes, then moisture cannot evaporate as easily, meaning you’ll feel hotter. 

• Reduce chafing: Because running clothing wicks sweat, the material stays drier. That avoids uncomfortable rubbing and chafing that can happen in clothes that retain moisture. 

• Breathability: Proper running clothing is ‘breathable’. This essentially means that it allows air to pass through it, which can help cool you down. Air can pass through the fibres of the fabric, and strategic ventilation in the underarm, back and inner thigh is also often used. 

• Tackle odours: Running in the heat means you sweat more. This can make clothing smellier. Proper running attire has special treatments which help prevent the build up of odour-producing bacteria. 

• Lightweight and loose-fitting: Running clothes for warm weather are especially lightweight and loose-fitting, which allows air to circulate. 

• Lighter colours: Summer running clothes tend to use lighter colour schemes - whites and pale tones reflect the sun’s rays, whereas dark colours absorb them. 

• UV protection: Some summer exercise gear has UPF treatments in the fabrics, which helps prevent sunburn through the clothes. 

Browse ASICS’ running clothing for men and women, and find gear that’s built for productive, enjoyable running in every season. 

4. Always use sun protection

The importance of sun protection when running in heat cannot be stressed enough. Ultraviolet rays are usually strongest between 11am and 3pm (it varies somewhat depending on where you live) and so the easiest way to avoid sunburn when running in the heat is to exercise outside of these hours. That being said, you can still be exposed to damaging rays earlier or later in the day, so you should take precautions whatever time you run:

• Always wear sunscreen: Sunscreen helps protect your skin against UV rays. You might want to choose a sweat resistant sunscreen that won’t be displaced when you sweat. 

• Sunglasses: Wear sunglasses with proper UV protection to keep the sun’s strongest rays out of your eyes. 

• Hats: Choose running caps or visors that keep the sun off your face. 

• Prioritise longer clothes: Particularly if you burn easily, choose running clothes with long sleeves and trousers. Breathable leggings and base layers can also be a good option. 

5. Adjust your running schedule

One of the great benefits of running in heat is that the days tend to be longer - particularly in countries in northern latitudes like the UK. On days that are forecast to be especially hot, try running first thing in the morning or in the early evening. You’ll still have plenty of light and warmth, but the air temperature will be several degrees lower, making it more comfortable for running in. 

Suggested: How to create a training calendar

6. Plan your running to reduce risk

There are things you can do to plan safer runs when it’s hot:

Avoid:

• Running primarily on asphalt and tarmac - these materials absorb heat and the surrounding air temperature will feel much hotter. 

• Remote locations - it’s good to be near people in case you suffer from heat exhaustion and need help. 

• Exposed locations - routes that offer little or no shade mean you have a higher risk of overheating. 

Try to:

• Follow shaded routes - this will reduce direct exposure to sunlight and mean you stay cooler. 

• Run near greenery and water - the air temperature around bodies of water (rivers, canals, lakes…) and greenery tends to be cooler. 

• Run where you can get water - follow routes where you know there will be public fountains or shops. 

• Run indoors when it’s extremely hot - during unusual heatwaves, it’s better to run indoors in an air-conditioned environment. 

7. Avoid intense runs on the hottest days

Hard, intense runs - be that distance races or interval training - will put your body under more stress than normal.Our bodies struggle to perform as well in high temperatures, and so doing especially intense exercise can do more harm than good. When running in heat, aim for shorter and slower jogs - keep the harder sessions for cooler days or early mornings in summer. 

Learn more: How to cool down after a race

Enjoy safe running in the heat

Running in the heat can be enjoyable, fun, and could even help improve your performance. However, it’s important to beware of the risks of warm weather training and take precautions. By following our tips for running in the heat, you can enjoy training year round while staying safe. 

Frequently asked questions about running in heat

We’ve answered some of the most common questions about running in the heat.

Is It Better to Run in the Cold or Heat?

Running in the heat and running in the cold both have advantages and disadvantages and so it ultimately depends on your personal preferences, as well as health considerations. 

Many people find they can run further in the cold, and it comes with a lower risk of dehydration. But it can also be uncomfortable, you need to layer up your running clothes, and there are risks of things like slipping on ice. 

On the other hand, running in the heat may feel more comfortable, helps your body produce Vitamin D and could help with performance. But of course it comes with risks such as dehydration, heat stroke and sunburn. 

Can running in the heat have any negative effects on my health?

Yes, running in the heat without proper preparation can increase your risk of a variety of health problems. Common issues include dehydration and mild sunburn. More severe issues include heat exhaustion, severe sunburn, seizures, kidney damage and brain damage. The greatest risks are associated with heart problems and heat stroke which can, potentially, kill. 

How do I recover after a hot weather run?

Strategies for recovery after a hot weather run include rehydrating with water, having a drink that contains electrolytes and resting. Taking a cold shower and wiping yourself with a damp, wet towe, can also be pleasant. 

Should I adjust my running pace when it's hot outside?

Yes, it’s generally recommended that runners go at a slower pace when running in heat. This is because your body is working harder to keep your core temperature stable, so overly-intense running can cause exhaustion. 

Is there a maximum temperature at which I should avoid running altogether for safety reasons?

While this somewhat depends on your experience of running in heat, your fitness level and other factors, there are heat stress risk indexes which can be used to assess how dangerous a workout could be. One index from the American Sport Education Program provides the following recommendations:

What should I do if I start to feel lightheaded or dizzy during a hot-weather run?

If you start to feel lightheaded or dizzy during a run in the heat, these could be symptoms of heat exhaustion. You should:

• Stop running immediately and rest

• Drink plenty of water

• Drink a sports drink containing electrolytes

• Get into the shade

• Monitor yourself for symptoms of heat stroke and seek medical attention if your symptoms deteriorate

• Loosen your clothing

• Take a cool shower or bath