Heatwaves Turn Life Upside Down

- At least one heat storm hits the Earth daily for more than 18 consecutive years

Heat waves have shifted from isolated, sporadic phenomena to severe, consecutive weather events that can cover vast areas of the planet for months, and sometimes years.

To understand the new reality of these heat waves extending over large portions of the globe, Reuters consulted with 24 climate researchers and analyzed global temperatures on an hourly basis for every day since 1960. From these findings, we derived a new concept: the "heat storm."

Scientists and researchers often discuss global warming in terms of the risks that would arise if the Earth's average temperature rises more than two degrees Celsius above pre-industrial levels. But what does that mean for the average person? Not much.

However, extreme heat waves used to be rare. They are no longer; they are now sweeping across the planet.

Anthony Leiserowitz, director of the Yale Program on Climate Change Communication, told Reuters that naming weather phenomena is "a powerful way for people to understand that something is happening." But he added, "We don't do that with heat waves," despite estimates indicating that heat kills nearly half a million people annually.

Below are the key findings of Reuters' extensive investigation into the "era of heat storms":

There is no single global definition of a heat wave. Therefore, in consultation with climate scientists, Reuters defined a standard heat wave as temperatures rising abnormally for five consecutive days or more. "Heat storms" are applied to the most extreme heat waves, those that cover at least one percent of the Earth's surface at their peak—an area roughly equivalent to half the size of Canada.

Heat storms were rare in the 1960s, averaging about five active storms per year. In contrast, during the current decade, the average has reached approximately 102 storms annually. One such storm caused the deadly heat wave that struck Europe this summer.

The largest recorded heat storm, named "Heat Storm Vera," lasted 367 days during 2023 and 2024, engulfing nearly 85 percent of the Earth's surface.

Reuters details how "Vera" impacted the world, from a soccer player hospitalized in Texas, USA, to Amazon river dolphins that perished in what was described as a "death circus," to cocoa farms in Côte d'Ivoire whose livelihoods were destroyed.

As greenhouse gas emissions have risen, so too have heat storms and standard heat waves. From the 1960s to the current decade, atmospheric carbon dioxide levels increased by more than 30 percent. During that same period, the average portion of the planet likely to be covered by heat storms and heat waves rose by more than twelvefold.

Reuters also identified a new phenomenon: heat storms occurring consecutively, simultaneously, or both, known as "heat storm chains." The duration of these chains increased from an average of about two months in the 1960s to nine months in the early 2000s.

After that, a chain began on July 6, 2008, and continues to this day. For more than 18 consecutive years, at least one heat storm has hit the Earth daily, and often more than one.

The world is currently under the influence of Heatwave Raymondo, which has exhausted Europe and contributed to igniting massive forest fires in Spain and France this summer. Since its onset on February 28, 2026, Raymondo has covered nearly three-quarters of the planet’s surface.

As part of this series, Reuters has created an electronic tool called the Heatwave Tracker, which monitors heatwaves in real time. It is now a feature of the Reuters Climate Observatory, which provides tools for understanding major weather phenomena and measuring the extent of global warming.