Doctors Warn Extreme Heat Can Cause Organ Failure

The human body strives to keep a core temperature of around 37°C, the point at which it has evolved to function. As the surroundings grow hotter, blood vessels widen to release heat through the skin, while sweat cools the body as it evaporates. But dilated blood vessels lower blood pressure and force the heart to work harder, and heavy sweating drains fluids and salt, upsetting their balance. This can trigger heat exhaustion — dizziness, nausea, headaches, cramps and confusion. If the person is not cooled within about 30 minutes, the condition can escalate into heat stroke, a medical emergency in which body temperature exceeds 40°C and sweating may stop altogether. Dr Rowley Cottingham, an emergency medicine consultant, warned that the body is then "literally cooking," as heat damages proteins in every organ.

The results can be fatal: brain swelling, organ failure, seizures, coma and death may follow within minutes if treatment is delayed. Heat already kills in large numbers — England recorded an estimated 2,985 excess deaths in the summer of 2022, when temperatures hit a record 40.3°C, and roughly 1,504 heat-associated deaths last summer. Most stem from heart attacks and strokes caused by the strain of regulating temperature, with risk rising once readings pass 25–26°C. The elderly, infants, and people with heart disease, diabetes or dementia are most vulnerable, as are the homeless and those in top-floor flats. Experts urge simple steps: staying indoors during peak hours, drinking water, wearing loose clothing, and quickly cooling anyone who falls ill before the damage becomes irreversible.