A study published in June in the journal Nature Climate Change reveals that global thermal stress has risen dramatically since the 1970s, and its conclusions resonate particularly strongly in Cuba, where extreme heat combines with prolonged blackouts and an energy crisis that hinders access to cooling.
The research, titled "Global heat stress intensification and its expanding footprint on the human population", was shared by the official media outlet Cubadebate, which summarized its central finding: "Thermal stress is changing not only in intensity but also in frequency, duration, and geographic extent."
The study uses the Universal Thermal Climate Index (UTCI), which combines temperature, humidity, wind, and solar radiation to measure how the human body actually perceives the environment, and analyzes data from the period 1970-2024 from the Copernicus Climate Change Service.
Among its most striking data: the proportion of the global population exposed to at least one day of extreme heat stress per year increased from 16% to 22%, which amounts to approximately one billion additional people.
Additionally, those who experience at least 90 days of severe thermal stress per year have increased from 55% to 70% of the global population.
In the subtropical regions —including the Caribbean— there are recorded up to 50 more days per year with extreme thermal stress than in the 1970s, according to the study.
A concerning fact that exacerbates the situation is nocturnal behavior: warmer nights are warming faster than the hottest days, at a rate of 0.32 °C per decade compared to 0.27 °C per decade, which reduces the body's recovery time.
For Cuba, the local context makes these global figures take on an even more urgent dimension.
A study from the University of Albany identified Cuba, Haiti, Puerto Rico, and the Dominican Republic as the Caribbean locations showing the clearest signs of increasing heat waves. The regional forecast CARICOF projected between 15 and 21 days of intense heat episodes in much of the island during the period from April to September 2026, with August and September being the most critical months.
The ongoing summer has confirmed these projections with concrete records: Camagüey recorded 38.1 °C on July 30 at the Ignacio Agramonte airport, surpassing the previous record of 36.0 °C set in July 1963.
Weeks earlier, La Palma, in Pinar del Río, recorded 37.6 °C on June 13, a historic record for that station and for the province in that month.
In June, the Sahara dust added to those extremes, which intensified the temperature sensation in Cuba amidst the power outages.
Previous research has documented that heatwaves cause an excess of mortality on the island, particularly among the elderly, children, pregnant women, and patients with chronic illnesses, and that heatwaves are leaving increasingly visible marks in Cuba, according to specialists cited by local media.
The United Nations warned in May 2026 that there is a 91% probability that at least one year between 2026 and 2030 will temporarily exceed the threshold of 1.5 °C above pre-industrial levels, indicating that the scenario described in the Nature Climate Change study will continue to worsen in the coming years.
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