Heat stress rises by up to two months in Mexico, Kenya, Italy, study finds

London,UPDATED: Jun 23, 2026 11:54 IST

A new study has found that Mexico, Kenya, Italy and several other parts of the world are now experiencing one to two more months of heat stress than they did a few decades ago, while some regions are seeing even bigger increases. Areas that were previously largely untouched by heat stress are also beginning to experience it, the research published in Nature Climate Change on Monday said.

The study said extreme feels-like temperatures, heat stress days and tropical nights have become far more frequent, longer and more severe over the past six decades as planetary warming intensifies because of the burning of fossil fuels such as coal, oil and gas. The researchers said they looked beyond air temperature alone and used feels-like temperatures to better understand the impact on people.

The team assessed heat stress on individuals by examining factors such as temperature, humidity and wind speed, using the Universal Thermal Climate Index to model how the human body responds to the environment. The study noted that heat combined with humidity can be dangerous because humidity affects how sweat evaporates, reducing the body's ability to cool itself. It said humid heat waves can be more deadly than dry heat waves because people do not cool down as easily.

While earlier studies have examined how human-driven climate change has pushed up temperatures, especially in recent years, this research focused on three levels of heat stress: strong, at index temperatures of at least 32 degrees Celsius; very strong, at at least 38 degrees Celsius; and extreme, at at least 46 degrees Celsius. The report comes amid other findings that people worldwide suffered an average of 41 extra days of dangerous heat in 2024 and that the world is on track to add nearly two months of extremely hot days each year by the end of the century.

The study found that parts of Southern Africa, including areas in Namibia and Angola, Eastern Africa including parts of Tanzania, Kenya and Uganda, and parts of Mexico and Central America could see about 50 more days a year of at least strong heat stress compared with the 1970s. In Southern Spain, Italy, Greece and Turkey, some areas are projected to experience up to 40 additional days of strong heat stress, while much of Southern Europe is already seeing almost a full extra month of such days compared with decades ago. In the United States, much of the country is seeing 15 or more days of at least strong heat stress, and southern areas including Texas and Florida are seeing close to 25 or more days of very strong heat stress.

The research also said heat stress seasons are lasting longer. Rebecca Emerton, the study's lead author and a senior scientist at the European Centre for Medium-Range Weather Forecasts in the United Kingdom, said it was striking "to see heat stress not only intensifying in those places that we already consider as being hot or used to experiencing heat waves... but also to see this, we call it, expanding footprint of heat stress expanding into regions where it's historically been rare or non-existent."

According to the study, feels-like temperatures on the 10 warmest nights of the year have risen faster, by 0.32 degrees Celsius per decade, than the 10 warmest days, which rose by 0.27 degrees Celsius per decade. For tropical nights, the researchers used a minimum temperature of 20 degrees Celsius, pointing to the risk that people may not be recovering properly from daytime heat during the night. The study added that one billion more people now face at least one day of extreme heat stress each year than they did in the 1970s.

Jennifer Francis, a climate scientist at the Woodwell Climate Research Centre on Cape Cod who was not involved in the study, said the world has long known that adding heat-trapping gases to the atmosphere by burning fossil fuels and cutting down forests would warm the globe. "This study adds stark details about increasing dangers to billions of humans," Francis said. "This analysis shows not only is temperature rising, but so is humidity, which makes high temperatures more deadly because our body's air conditioning system - sweating - struggles to keep up." Emerton said the findings highlight the need to limit future warming and ensure adaptation strategies, heat health action plans, early warning systems and climate risk assessments are in place. Overall, the study said heat stress is worsening, lasting longer and spreading into more parts of the world than before.

With PTI Inputs

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