Heatwaves are becoming global "heat storms”: 102 episodes annually, compared to five in the 1960s

An extreme heat phenomenon covered nearly 85% of the Earth's surface over the course of 367 days. Reuters warns that these large-scale episodes impact public health, agriculture, and ecosystems. Heatwaves are no longer merely local meteorological events, confined to a few days and specific regions. An analysis by Reuters reveals that, in recent decades, they have evolved into planetary-scale phenomena that can persist for months and simultaneously affect territories thousands of kilometers apart. The news agency proposes the term "heat storms” for the most extensive episodes of unusually high temperatures. According to the investigation, the frequency of these events has risen from approximately five per year in the 1960s to about 102 annually in the current decade.

• A phenomenon that can encompass nearly the entire planet

To identify these episodes, Reuters journalists analyzed global temperature data from 1960 to the present and consulted approximately two dozen experts in meteorology and climatology. The analysis incorporated hourly temperatures from over a million geographic grid cells covering the Earth's surface. In the methodology employed, a heatwave is defined as at least five consecutive days during which maximum temperatures exceed historical thresholds specific to each area. Such an episode is classified as a "heat storm" when the affected area reaches, at some point, at least 1% of the planet's surface. The difference in scale compared to the past is significant. In the 1960s, the largest heatwave identified in the analysis covered approximately 6% of the globe's surface and lasted 46 days. In contrast, the most extensive episode recorded in this decade persisted for 367 days and ended up affecting nearly 85% of the planet, including regions near the poles. The phenomenon, dubbed "Vera," unfolded between July 2023 and July 2024. According to Reuters, its effects were felt in widely disparate regions, from the Amazon to the Philippines and the southern United States.

• Effects on health, agriculture, and ecosystems

The scale of these phenomena is reflected in consequences that go beyond the discomfort caused by high temperatures. In the Philippines, the Vera episode exposed students in schools lacking air conditioning to dangerous conditions, with repeated instances of fainting and health issues linked to extreme heat. In the Amazon, high temperatures contributed to the excessive warming of Lake Tefe, where the water reached 41 degrees Celsius. More than 200 freshwater dolphins died in September and October 2023, according to reports cited by Reuters. Researchers identified signs of heat stress in the animals examined, while extreme temperatures and the drying up of part of the lake further compromised their survival. In other regions, prolonged heat episodes have fueled droughts and wildfires, impacted agricultural production, and placed strain on infrastructure. In Europe, heatwaves led to record-breaking temperatures in several cities this summer, with authorities reporting a high number of excess deaths linked to the heat. The Reuters investigation also highlights the connection between high temperatures and the vulnerability of ecosystems. Glaciers, agricultural crops, and freshwater species face heightened risks when periods of extreme heat are prolonged.

• Climate change amplifies risks

The increasing frequency of "heat storms" is part of a broader trend of global warming. According to the analysis, greenhouse gas emissions and El Niño events-characterized by the abnormal warming of waters in the equatorial Pacific-can contribute to the intensification of extreme weather phenomena. The data also point to a significant reduction in the areas affected by extreme cold. On an average winter day, the portion of the planet experiencing unusually cold weather has shrunk by nearly 80% compared to the 1960s, the investigation finds.

Reuters notes that these "heat storms" have occurred with increasing frequency and have increasingly overlapped. Since July 6, 2008, the planet has been continuously under the influence of at least one such storm-based on the criteria used in the analysis-with multiple phenomena sometimes unfolding simultaneously. A new episode, dubbed "Raimundo," began in February 2026 and, by the time of the analysis, had affected nearly three-quarters of the globe's surface. By the end of August, at its point of maximum extent, it covered 33.8% of the planet, according to Reuters.

• Naming the phenomena: a tool for understanding the danger

Beyond meteorological data, the Reuters initiative aims to change the way in which communicating climate risks. Currently, tropical storms and hurricanes are identified and tracked through naming systems, whereas heatwaves lack a comparable global mechanism. Anthony Leiserowitz, director of the Yale Program on Climate Change Communication, told Reuters that assigning names to weather phenomena can help the public more easily grasp the scale of an event and its consequences. By defining and monitoring heatwaves, researchers and journalists hope to provide authorities with a clearer tool for assessing risks and preparing protective measures for the population. The stakes are economic and social, not just environmental. Extreme temperatures can impact labor productivity, supply chains, agriculture, infrastructure, and healthcare system expenditures. As these episodes become more widespread and persistent, the ability of states to anticipate and mitigate their effects becomes a matter of economic security.