What a heatwave does to the body

A heatwave can cause dehydration and exhaustion. (Getty Images)
A heatwave can cause dehydration and exhaustion. (Getty Images) (Sandy Aknine)

While we are yet to experience a full-blown heatwave this summer, the Met Office recently revealed that the UK has seen its hottest June on record.

For June 2023, the average mean temperature was 15.8C across England, Wales, Scotland and Northern Ireland, eclipsing the last hottest June by 0.9C.

Last year, temperatures reached over 40C in some parts of England, but what can these heatwave temperatures really do to our body?

How does a heatwave affect the body?

The main risks are dehydration and overheating, which can lead to heat exhaustion or heat stroke.

Excessive sweating in the warm sun can trigger dehydration if the fluids are not replaced. Signs of dehydration include:

  • Excess thirst

  • Producing dark-coloured urine in small amounts

  • Dizziness

  • Fatigue

  • A dry mouth, eyes or lips

Children or babies may also seem drowsy, breathe quickly, produce few or no tears, have cold or blotchy hands and feet, and have a sunken fontanelle – the soft spot on an infant’s head. A child should be taken to A&E if they develop any of the above.

In adults, emergency treatment is needed if they become unusually tired, confused or disorientated; fail to urinate all day; develop a weak or rapid pulse; or have a seizure.

Overheating may come about if a person’s core temperature fluctuates too far from 37C (98F).

The body is typically very effective at regulating its temperature, but too much sun or strenuous activity can leave it unable to cool down. Heat cramps in the muscle are usually the first warning sign.

A young woman cools down with cold water during the summer heat.
Sweating can lead to dehydration during a heatwave. (Getty Images) (SimpleImages via Getty Images)

Without seeking shade, this can develop into heat exhaustion, a condition that causes heavy sweating and a rapid pulse.

Perhaps surprisingly, cool skin with goose bumps is a common symptom. Others include feeling faint or dizzy, fatigue, nausea, headaches, a loss of appetite and excessive thirst.

When taking a sufferer’s temperature, it may come back just marginally higher than normal at 38C (100F).

Children typically develop all of the above, as well as potentially becoming floppy.

Without treatment, heat exhaustion can lead to heat stroke, a potentially life-threatening disorder that occurs when the body reaches 40C (104F) or above. In severe cases, this can seriously damage the vital organs.

Although anyone can become ill from too much sun, at-risk groups include the elderly or very young, obese people, those on certain drugs and individuals who are not used to the heat.

Dehydration is also more common in those who have been vomiting or had diarrhoea, and diabetes patients.

How to stay safe in the sun

If you start to feel out of sorts, stop all activity and rest. Move to a cool place and sip cold water or a rehydration sports drink.

Lie down with your feet raised. If possible, cool the skin with a sponge or fan. Cold packs around the neck and armpits may also help.

Woman Drinking Water From Bottle At Railroad Station Platform
Drinking water helps ward off dehydration on a hot day. (Getty Images)

Most start to feel better with 30 minutes. If things do not improve after an hour, seek medical help immediately.

People should also call 999 if they are not sweating despite being hot, have a temperature of 40°C or above, are confused, breathe quickly or appear short of breath, have a seizure, lose consciousness or become unresponsive.

The good news is the sun can be enjoyed safely, with dehydration and overheating both being preventable.

While it may sound obvious, drink plenty of fluids. This will help your body produce sweat that cools you down.

Wear a broad-spectrum sunscreen, sunglasses and a wide-brimmed hat when out and about. Loose-fitting clothing will further protect you from the sun without causing overheating.

Take it easy on a hot day, rest frequently in the shade if exercising and allow yourself to adjust to the warm weather.

Try and also avoid being outdoors at the hottest time, typically between 11am and 3pm.

Remember to also never leave a child in a parked car on a warm day, even if the windows are open or it is in the shade.

Alcohol should also not be drunk excessively in the sun.