There are 27 ways hot weather can kill you. Here’s how to avoid them

This summer the news has been awash with alarming reports of deaths in countries all over the globe due to heat stroke. According to a recent report by the Intergovernmental Panel on Climate Change extreme heat events are increasing in frequency and duration and are affecting more people. Why is this happening and how can we spot if one of our friends or family are at risk?

What happens in our bodies when we overheat?

Heat stress is caused by a build-up of heat in our bodies because of exertion, for example running a 5k race or doing heavy manual tasks, or as a result of stressors from the external environment. It is affected by solar radiation, air temperature, relative humidity and wind speed. In addition, it is influenced by how used to a climate a particular person is (known as acclimatisation), the type of work they are doing, how much they are exerting themselves and the clothing they are wearing.

Humans are homotherms. This means that we must keep our internal core body temperature constant, at around 37°C. If our internal body temperature reaches around 42°C our vital organs begin to shut down. This can result in severe illness and even death. It is thought that there are 27 different pathways that a person can die from extreme heat. This includes reduced blood flow and damage to the brain, heart and lungs.

Those who are most at risk of heat stress progressing into heat illnesses are those who have a limit in their body’s ability to regulate the core body temperature, known as thermoregulation, and those who have less ability to seek and access cooling are more vulnerable. This includes babies and infants, children, the over 65s, those with preexisting medical conditions, pregnant women and outdoor workers.

What are heat illnesses?

Heat illnesses occur when the risk of heat stress is high, and someone begins to feel unwell. There are several different kinds of heat illnesses, and they often occur at the same time as dehydration. These include: ‘heat syncope’ – which results from excess sweating, ‘heat tetany’ – or hyperventilation, heat cramps and heat exhaustion.

Another common type of heat illness is heat stroke, which occurs when the body can no longer control its internal temperature. Heat stroke falls into two categories: exertional heat stroke, which occurs due to strenuous exercise, and classical heat stroke, which results from passive exposure to extreme environmental heat.

Read more:

What should I do if I think someone is experiencing heat stroke?

The first thing is, if someone passes out or is experiencing difficulty concentrating or breathing, you should seek immediate medical advice. If someone is fully conscious but feels unwell, overly hot or is feeling sick then they need to cool down and rehydrate as soon as possible.

The best way to cool someone down in the shortest time is to submerge them in cool water such as a bath, shower or swimming pool.

You must be careful not to use water that is too cold as this can result in cold shock which can cause sudden changes in breathing, heart rate and blood pressure. There is no benefit in using ice water.

If fully submerging someone suffering from heat stroke in water isn't an option, cooling their feet, hands or the back of their neck and face can also help to cool their core body temperature.

They will also need to replenish the minerals and water lost from their bodies through sweat due to overheating. This can be done by giving them a sports drink to replenish their body fluids, electrolytes, and salt.

How can you prevent heat illnesses?

In a lot of cases, heat illnesses are preventable. Many countries increasingly have heat health plans to issue warnings and prepare regions for periods of extreme heat. Typical advice given out includes staying out of the heat of the day by being in a cooler place between 12pm and 5pm and staying hydrated – contrary to popular belief hot drinks are just as effective as cold, the temperature has little influence on core body temperature.

You can also cool down by taking cold showers and cooling your hands, feet and face with cold water. Promoting airflow through your house by opening windows and doors, when the air temperature outside is cooler and not in the direct sunlight. Drawing curtains, blinds or shutters to shield indoor spaces from the heat of the Sun can also help to keep things cool as can the use of fans to circulate the air.

However, special care should be taken over the most vulnerable members of society. The elderly, for example, often underestimate their risk of developing heat stroke and are usually only more likely to drink more water, stay cooler or take it easy if family or friends advise them to.

Infants are also particularly vulnerable to extreme heat. A study carried out by researchers at the Heat and Health Research Incubator at The University of Sydney found that the most common strategy for keeping the Sun off babies is to place a light blanket over their prams. However, this can raise the temperature inside by 4°C in 20 minutes. A more effective method is to cover the pram with a damp cloth and use a small clip-on fan.

Is the situation going to get worse?

While extreme heat events are increasing thanks to climate change, heat policy has also made a lot of progress in recent years. In a lot of cases, governments have put detailed heat health plans in place. However, these are often more reactive than proactive. Other measures such as more thoughtful urban planning can also come into play. One example is to include green spaces in urban areas to help keep down temperatures where heat is highest thanks to the so-called urban heat island effect.

Anticipatory action such as providing funds for schemes like cooling centres where residents can take shelter during a heatwave through forecast-based financing and early warning systems that inform people of the impacts of heat and give them reminders on how to keep cool can also make a significant contribution.

However, the only way to effectively prevent extreme heat from increasing even more is to transition to net zero, where the carbon emitted into the Earth's atmosphere is equal to the carbon removed from it. This will stop emissions that are causing a rise in baseline temperature and prevent extreme events such as heat waves.

This is vitally important because as temperatures climb we could reach a threshold where even the healthiest person would be unable to survive without access to cooling. That's a future none of us want to see.