Organ failure, seizures and gallons of sweat: what happens to your body at 54C

Earth’s highest ever temperature may have been recorded on Sunday, when Death Valley in California reached highs of 54.4C (130F). Although it is a national park, the heat is so extreme that authorities are currently advising no-one goes walking there after 10am, and those outside to drink at least four litres of water every day.

This might sound like a far-off problem, but it’s not: in England, 2,000 people die from the heat each year, according to the NHS. The human body has to be very finely calibrated to a core temperature of around 37C to function correctly, and even changes of a degree or so either way can lead to organ damage and even death.

We look at how your body reacts to very high temperatures...

Extreme sweating

To keep itself in the Goldilocks zone of around 37C the body uses sweating, shivering, goosebumps and flushed skin to raise or lower its temperature. When you get too hot, your body releases sweat to cool down through evaporation.

In very high temperatures, it can get extremely difficult to replace the water lost through sweat because of the sheer quantity of it: manual labourers working in summer temperatures of 30-35C lose up to 12 litres of sweat a day, according to a 2008 study.

Sweat is not just water, either. The workers in this study also lost up to 15g of salt a day: two and a half times the recommended daily allowance.

If you do not replace all the water lost through sweat, you can become dehydrated, which can cause headaches, dizziness and tiredness. It will also put strain on your cardiovascular system: your blood volume may decrease, meaning your heart will need to beat faster to move oxygen and nutrients around your body.

Sweating is not as effective in very humid conditions, when the air is already saturated with water. You may feel like you sweat more on close and muggy days. This is not the case: you sweat the same amount but the sweat evaporates less quickly, leaving more on your skin at any one time.

Reduced blood flow to your organs

Another way your body tries to cool down is by dilating blood vessels close to the skin, in order to move heat away from the inside of your body. This extra blood flow close to your skin explains why you may get red in the face on a hot day.

The extra blood coming to the surface of your body means there is reduced flow to your inner organs. In compensation, your heart beat may beat faster, to supply the muscles and organs with enough blood.  In prolonged exposure to very high temperatures, some people will suffer organ failure, and potentially death.

You may also vomit, feel nauseous or have a stomach upset in temperatures like those in Death Valley, as your digestive system experiences disruption from decreased blood flow.

Breathing rate

For many mammals, panting is the most important way to keep cool in the summer or after exercise. It works in two ways: firstly, heat leaves their body through evaporation of moisture in the mouth. Panting is also a sort of natural air conditioning, as it rapidly replaces hot air in the lungs with slightly cooler air from outside.

Humans have evolved to be able to sweat, which reduces our need to pant. However, we do still breathe faster in extreme hot weather, so Death Valley may leave you panting like a dog. This may partly be a way to cool us down, with research suggesting that the colder air breathed in may help to regulate specific areas of the brain. However, you may also be breathing faster to get in added oxygen which can fuel the body’s cooling efforts.

Brain

Extreme heat takes its toll on the brain. In extreme cases, people can feel disorientated and confused, as their brain struggles to function properly. Sometimes, these effects can be permanent, and not go away when you cool down. In worst case scenarios, people may have seizures or lose consciousness.

In 2009, three people died after being exposed to temperatures of up to 50 degrees for hours in a new age retreat in Arizona, USA. This was part of a “sweat lodge” exercise, where hot rocks were piled inside a tent in the desert. Water was poured over the rocks to create steam. The three lost consciousness as their brains struggled to cope with the high temperatures.

Very high temperatures also negatively affect your mental wellbeing. Research shows that on the hottest days of the year there is an increase in the number of suicides and violent attacks, as intense heat can affect parts of the brain that regulate emotions.