High temperatures during summer months can lead to a notable increase in excess deaths, with data from 2022 indicating a substantial rise in mortality coinciding with record-breaking heat. In that year, England recorded temperatures of 40.3C, and an estimated 2,985 excess deaths were attributed to the heat. Similar patterns were observed in subsequent years, with an estimated 1,311 heat-associated deaths during summer 2024 and 1,504 during summer 2025.
The primary cause for these heat-related fatalities is the strain placed on the body as it attempts to maintain a stable internal temperature, often leading to heart attacks and strokes. The increased death rate typically begins once temperatures consistently surpass 25C to 26C. However, evidence suggests that the most significant impact may stem from higher temperatures experienced in the spring or early summer, rather than during the peak of the summer season.
One theory for this phenomenon is that individuals may adapt their behavior and routines as the summer progresses, becoming more accustomed to and better equipped to handle warmer conditions. The impact of heatwaves on mortality appears to be rapid, with an increase in deaths often occurring within the first 24 hours of a heatwave beginning. While hot weather poses risks to everyone, certain individuals are at a greater risk of severe health consequences.
Heat can affect the body in various ways, including causing feelings of dizziness or faintness due to dehydration, increasing heart rate, inducing sweating, and leading to swollen ankles. In more severe cases, it can escalate to heat exhaustion, characterized by symptoms such as excessive sweating, clammy skin, nausea, vomiting, and muscle cramps. If left untreated, heat exhaustion can progress to heatstroke, a life-threatening condition. Heatstroke is identified by symptoms like confusion, a lack of sweating, hot and dry skin, a body temperature exceeding 40C, nausea, vomiting, and potentially loss of consciousness, convulsions, or seizures. ![A graphic showing the differences between heat exhaustion and heatstroke. Heat exhaustion symptoms are listed as: feeling faint or dizzy; excessive sweating; clammy skin; nausea or vomiting, and muscle cramps. Heatstroke symptoms are: feeling confused; not sweating; a body temperature above 40C with hot with dry skin; nausea or vomiting; may lose consciousness or experience convulsions or seizures.