More than 5,100 people in Germany died from heat-related causes by the end of June 2026, according to the Robert Koch Institute (RKI). But how do researchers prove that someone died because of soaring temperatures? Heatstroke begins with headaches, dizziness and loss of awareness. The body's regulation system fails, causing body temperature to rise to life-threatening levels, leading to multiple organ failure and death. Doctors rarely record deaths directly attributable to heat.
According to Germany's Federal Statistical Office, an average of 21 such cases were recorded each year between 2004 and 2014. Therefore, the 5,120 heat-related deaths reported by the RKI is an estimate. However, the figure is not pulled out of thin air. "It is based on a statistical correlation," says Alexandra Schneider, a meteorologist, epidemiologist and deputy director of the Institute of Epidemiology at Helmholtz Munich.
The estimate was derived by comparing death figures from the Federal Statistical Office with temperature trends measured by the German Weather Service. In the final week of June alone, around 23,600 people died. The weekly average temperature was 26 degrees Celsius. The RKI assumes that heat-related deaths occur from a weekly average temperature of 20 degrees Celsius onward.
The number of deaths in that final week was nearly 30% higher than the average for comparable periods in previous years, when around 18,200 people died. To estimate heat-related deaths, researchers modeled how many deaths would have occurred under conditions with temperatures of no more than 20 degrees Celsius. Researchers also adjust for certain confounding factors, Schneider explains. Using this method, the RKI estimates 5,120 heat-related deaths, with 4,310 occurring in the final week of June alone.
Schneider considers the estimate plausible and says she expected a figure of this magnitude. She has previously criticized the RKI's methodology. "If temperatures fluctuate sharply within a week, using a weekly average can smooth out those extremes and lead to an underestimation of deaths," she explains. "This time, however, it was consistently hot."
The same applies to cold-related deaths: they are estimates based on a plausible statistical link. During colder months, respiratory illnesses become more common. Cold temperatures also contribute to cardiovascular diseases, just as heat does, explains Schneider. "In Europe, cold-associated mortality is still far higher than heat-associated mortality," Schneider says. "But we are seeing a slow shift."
Could climate change lead to milder winters and therefore fewer deaths? Researchers have also looked into this question and modeled different scenarios. Regardless of how favorable the scenarios are, Schneider says, they all point to the same conclusion: "the net effect — meaning the total number of deaths — increases." This is because the rise in deaths attributed to heat is so significant that it cannot be offset by the decline in cold-associated deaths.
Schneider says that focusing solely on heatstroke as a cause of death linked to high temperatures would massively underplay the impact of heat. "That is why these statistical methods are used to identify and examine links between heat and other chronic diseases." She herself has contributed to studies showing a connection between heat and certain illnesses. "We were able to show that heat is now strongly associated with heart attacks," Schneider says. Nighttime heat also increases the risk of strokes.
Jonas Sonnenstuhl is a paramedic in Teltow, Brandenburg. "We all know that conditions like strokes and heart attacks become more frequent and can also become life-threatening more quickly," he says. Schneider describes heat-related deaths as only the tip of the iceberg. Even when high temperatures do not lead to death, they place a strain on people's health — especially those with pre-existing conditions.
Sonnenstuhl recalls a 17-year-old patient with a congenital heart defect who called emergency services during the heatwave. "She showed clear symptoms that day, which could already be traced back to the fact that her body was at its limit." Shortness of breath, dizziness and impaired consciousness. The heat also pushed emergency responders and hospital staff to their physical limits. On June 28, when Sonnenstuhl was working a 24-hour shift, the temperature inside the ambulance did not fall below 30 degrees Celsius.
Many hospital emergency departments are not air-conditioned, and emergency stations are even less likely to be, Sonnenstuhl says. "Both we and the hospital staff were at our limit." For people whose job is to save lives, he says, staying cool in an emergency is essential.
Source: www.dw.com