Dr Angela Rai, GP at The London General Practice, spoke exclusively to Express.co.uk about heat exhaustion, sunstroke, and the health risks. “Being exposed to too much heat can lead to you feeling generally unwell, lacking in energy and feeling dizzy or sick,” said Dr Rai.

This is typically a sign of heat exhaustion, which may also lead to other unsettling symptoms. Should you notice any signs of heat exhaustion, it’s key to take the right care steps to prevent it turning into sunstroke. “Sunstroke is the most serious form of heat injury and is a medical emergency,” warned Dr Rai.

Heat exhaustion symptoms:

• Headaches
• Loss of appetite
• Nausea
• Body temperature about 38C
• Excessive sweating
• Pale, clammy skin
• Feeling very thirsty

“Heat exhaustion should be treated quickly to prevent it turning into heatstroke,” said Dr Rai. The person affected needs to be moved to a cooler place out of direct sunlight.

They should then lie down and raise their feet slightly, and sip on a sports drink or oral rehydration sachets.

“Cool their skin with water using a spray or sponge,” added Dr Rai, adding that the person should “feel better” within half hour.

If the symptoms persist, “it is best to seek medical attention and if in doubt call 999”.

Signs of sunstroke:

• Body temperature above 40C
• Fast breathing
• Shortness of breath
• Feeling unwell after resting and cooling off
• Feeling confused
• Having a seizure
• Loss of consciousness
• Not being responsive

Sunstroke occurs when the body is unable to regulate the internal temperature.

Dehydration occurs which leads to electrolyte imbalances and, in severe cases, problems with kidney function, cardiac abnormalities and dangerous heart rhythms.

There could even be “damage to brain tissue due to brain haemorrhage or swelling”.

If you are unsure whether you could be suffering from heat exhaustion or, indeed, the beginning of sunstroke, call 111.

Do follow the advice of the emergency response team who might encourage you to visit a hospital.