A heatstroke begins with headaches, dizziness and loss of awareness. The body’s regulation system fails, causing body temperature to rise to life-threatening levels. Multiple organ failure and death can follow. But doctors rarely record deaths that can be directly attributed to heat. According to Germany’s Federal Statistical Office, an average of 21 such cases were recorded each year between 2004 and 2014.
The 5,120 heat-related deaths in Germany in 2026 through June 28, published by the Robert Koch Institute (RKI), is therefore an estimate. But that does not mean the figure is 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.
Statistical link between temperatures and deaths
This estimate was found by comparing death figures collected by Germany’s Federal Statistical Office with temperature trends over a given period measured by the German Weather Service. In the final week of June alone, around 23,600 people died. The weekly average temperature — meaning the average daytime and nighttime temperature over the course of a week — was 26 degrees Celsius. The RKI assumes that heat-related deaths occur from a weekly average temperature of 20 degrees Celsius onward.
How to survive heat waves in the city
To view this video please enable JavaScript, and consider upgrading to a web browser that supports HTML5 video
The number of deaths in that final week of June was nearly 30% higher than the average for comparable periods in previous years, when around 18,200 people died. To estimate the number of 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 that there were 5,120 heat-related deaths — with 4,310 of those occurring in the final week of June alone.
Heatwaves are particularly challenging for people who work outdoorsImage: Benjamin Westhoff/dpa/picture alliance
Alexandra Schneider considers the estimate plausible and says she expected a figure of this magnitude. In the past, the epidemiologist has 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.”
More deaths linked to cold than heat in Germany and Europe
The same applies to cold-related deaths as to heat-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 epidemiologist Schneider.
“In Europe, cold-associated mortality is still far higher than heat-associated mortality,” Schneider says. “But we are seeing a slow shift.” Couldclimate change perhaps 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 can’t be offset by the decline in cold-associated deaths.
Heat-related deaths are only the tip of the iceberg
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.
How to deal with a heatstroke
To view this video please enable JavaScript, and consider upgrading to a web browser that supports HTML5 video
Heat strains emergency responders and hospital staff
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.
Alexandra 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. Heavy protective clothing, steel-toe boots and physically demanding work added to the strain.
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.
This article was originally published in German.
