Workplaces need heat policies to stop employees’ body temperatures from reaching dangerous levels, a major report from the United Nations’ health and weather agencies said today.

After the hottest year on record in 2024, extreme heat is “for many, a case of adapt or die,” Johan Stander of the World Meteorological Organization told reporters at a press conference Thursday.

More than 2.4 billion workers are exposed to workplace heat stress, according to the International Labour Organization, putting them at greater risk of heat stroke, kidney and cardiovascular disease. The U.N. labor agency also estimates that heat stress leads to more than 22 million occupational injuries and almost 19,000 fatalities every year.

Artificial climate change, driven by the burning of fossil fuels, is causing more frequent and intense heat waves. According to the Intergovernmental Panel on Climate Change, every additional 0.5 degrees Celsius of global warming significantly raises the risk of longer and worse heat waves.

Workers are the single largest group vulnerable to climate change, the U.N. report said, with nearly every sector affected by higher ambient temperatures. Outdoor workers and first responders are especially vulnerable, but so too are indoor workers in heat-intensive industries.

“If your body has a temperature of 38 degrees … over a longer period of time, that is when the risk starts to be very high,” said Rüdiger Krech, director for environment and climate change at the World Health Organization.

At that point, heat is no longer a “discomfort” but a serious health threat, with the poorest workers being most at risk, he added.

“The workers keeping our societies running are paying the highest price. The impacts are especially severe in vulnerable communities with limited access to cooling, health care and protective labor policies,” Krech said.

Heat also has a marked effect on labor productivity, the report found, with a 2–3 percent drop off for every degree above 20 C.

European trade unions have called on the European Commission to propose a directive on maximum working temperatures, in response to a 42 percent rise in heat-related workplace deaths in the EU since 2000. POLITICO has contacted the Commission for comment.

Statutory heat protections vary across EU countries. In Spain, office temperatures must be between 17 C and 27 C, while Cyprus earlier this month banned outside work between 12 p.m. and 4 p.m. in areas under severe weather warnings. 

Extreme heat may often be termed a “silent killer,” Stander said, “but with today’s science, data and technologies, silence is no longer an excuse. Almost all heat illness, injury and death is preventable if we use tools and information.”