Understanding Heat Stroke: Vital Information for the UK’s Current Heatwave

As the UK faces scorching temperatures, medical professionals emphasize the importance of recognizing heat stroke symptoms and taking immediate action.

The UK is currently experiencing a severe heatwave, with temperatures soaring towards the high 30s in parts of England and Wales. As the nation swelters under this intense heat, medical experts are urging the public to be aware of the danger signs of heat stroke a life-threatening condition that can become fatal within hours if not treated promptly.

The Met Office has issued extreme heat warnings, and health officials are cautioning that the soaring temperatures pose risks not only to the elderly and vulnerable but also to healthy adults and children who may become overheated or dehydrated. Last summer, there were approximately 1,504 heat-associated deaths in England during five heat episodes, according to figures from the UK Health Security Agency (UKHSA).

The Distinction Between Heat Stroke and Heat Exhaustion

Heat stroke can manifest in two ways: through intense physical activity in extreme heat or gradual exposure to high temperatures. Heat exhaustion often precedes heat stroke and requires immediate attention to prevent it from escalating.

Common symptoms of heat exhaustion include a high temperature, extreme thirst due to dehydration, irritability, and confusion. Affected individuals may also experience fatigue, dizziness, headaches, nausea, excessive sweating, pale or clammy skin, and muscle cramps. To prevent heat exhaustion from progressing to heat stroke, the NHS recommends moving the affected person to a cool place, removing unnecessary clothing, and encouraging them to drink plenty of water or rehydration drinks containing electrolytes. Cooling the skin with cool water, ice packs, or damp cloths can also be beneficial.

If symptoms do not improve within 30 minutes, emergency medical help should be sought immediately, as the condition may have progressed to heat stroke. Dr. Ann Nainan, a GP specializing in urgent care, emphasizes, ‘The sooner you cool down, the less damage will be done.’

The Body’s Response to Extreme Heat

With large parts of the UK experiencing temperatures above 35C, experts warn that just five minutes in these conditions can have significant impacts on the body. Dr. Nainan explains that the body begins working harder almost immediately to maintain its natural temperature of around 37.3C. As temperatures rise, the heart rate increases, and sweat production intensifies in an attempt to lower the body’s temperature.

This process can lead to fluid loss and dehydration, especially if a person is exposed to direct sunlight or not drinking enough water. At this early stage, experts recommend wearing loose, lightweight clothing, applying sunscreen, and drinking water regularly to replace fluids lost through sweating. If no action is taken, discomfort can set in after just 10 minutes, with sweat becoming more intense and dehydration beginning to set in. Headaches can even be felt at this point. Fortunately, this can be prevented with just a few minutes in the shade and a drink of cool water.

Intensifying Effects After 10-40 Minutes

If no preventative measures are taken, the effects of extreme heat can become more intense after just 10 to 20 minutes. At this point, the body is using significant energy resources to cool down, and feelings of thirst and skin burning (if no sunscreen has been applied) become more noticeable. By around 40 minutes, many people could begin experiencing the early stages of heat exhaustion.

Dr. Nainan warns that individuals may start feeling symptoms such as cramps and spasms due to a lack of electrolytes in the body. Other warning signs at this stage include headaches, nausea, dizziness, and persistent sweating. Without taking action—such as moving into the shade, finding a cool space, and rehydrating—the risk of developing heat stroke becomes very real.

The Critical Hour Mark

By spending an hour exposed to extreme heat, experts warn that the body’s temperature can rise beyond its normal level to 38.5C, a condition known as hyperthermia. This can bring on heat exhaustion, which can sometimes turn into heat stroke. At this point, Dr. Rowley Cottingham, a director of the British Association for Immediate Care and a consultant in emergency medicine, says people will begin to feel incredibly tired and have an overwhelming desire to stop everything.

It is crucial to prevent the condition from worsening. If shaded or cool shelter is unavailable, soaking clothing with water can help lower body temperature, while taking small, frequent sips of water can aid rehydration. Eating foods rich in electrolytes—such as bananas, watermelon, and salty snacks—can also help replace minerals lost through intense sweating. If symptoms persist or worsen despite these steps, medical advice should be sought immediately to prevent heat stroke.

The Onset of Heat Stroke

If no preventative measures are taken—or if they are not effective—the body will enter a state of heat stroke within 90 minutes to two hours. Having failed to cool itself down, the body’s temperature can rise to 40C, triggering brain, heart, and liver malfunction, and potentially leading to death within minutes.

Dr. Cottingham describes the danger: ‘It’s incredibly dangerous: it kills very quickly. You’re literally cooking like an egg. Body proteins suffer heat damage, and this happens to every organ.’ The brain is first affected after swelling in the heat, which is often why heat stroke sufferers feel confusion. This can be followed by struggles with balance and coordination, while their skin often becomes hot and dry to the touch.

Sweating may stop altogether as the body’s cooling system breaks down. Other symptoms can include a rapid heartbeat, dizziness, weakness, nerve dysfunction, and an increased risk of fainting. As heat stroke takes hold, the consequences become increasingly severe. Loss of consciousness can occur, and the most serious cases may lead to seizures, coma, and, ultimately, death if treatment is not provided urgently.