Extreme Heat Can Cause Organ Failure, Doctors Warn

The human body tries to keep a core temperature of about 37°C. When it gets hotter, blood vessels widen to release heat, and sweat cools the body as it evaporates. But wider vessels lower blood pressure and make the heart work harder, while heavy sweating drains fluids and salt. This can cause heat exhaustion — dizziness, nausea, cramps and confusion. If the person is not cooled within about 30 minutes, it can become heat stroke, an emergency in which body temperature passes 40°C and sweating may stop. The body is then "literally cooking," as heat damages proteins in every organ.

The results can be deadly: brain swelling, organ failure, seizures, coma and death may follow within minutes. Heat already kills many people — England recorded about 2,985 extra deaths in the summer of 2022, when temperatures hit a record 40.3°C, and around 1,504 heat-related deaths last summer. Most come from heart attacks and strokes, with risk rising once temperatures pass 25–26°C. The elderly, infants, and people with heart disease, diabetes or dementia are most at risk, along with the homeless. Experts urge people to stay indoors during peak hours, drink water, and quickly cool anyone who falls ill.