Human-Driven Climate Change Amplifies Deadly Heatwave in Mexico and US by 35 Times

New findings from World Weather Attribution (WWA) reveal that human-driven global warming increased the likelihood of a recent lethal heatwave across Mexico, Central America, and the southern United States by a factor of 35.

Magnitude and Reach of the Heatwave

Over recent weeks, an expansive heat dome—a region of elevated atmospheric pressure—has trapped scorching air over Mexico and extended north into Texas, Arizona, and Nevada, as well as southward into Belize, Honduras, Guatemala, and El Salvador, subjecting tens of millions to extreme heat.

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By trapping hot air near the surface and blocking the influx of cooler breezes, the heat dome sustained dangerous temperatures, shattering multiple daily and nationwide records in May and early June. This prolonged heat has had devastating effects, particularly for impoverished and vulnerable groups.

The WWA report indicates such powerful heatwaves are now four times more common than around 2000, when global temperatures were roughly 0.5°C cooler. Friederike Otto, a study co-author and senior climate scientist at Imperial College London's Grantham Institute, stressed the mounting danger of heatwaves, attributing continued fossil fuel use to political reluctance despite decades of warnings.

Health Consequences and Strain on Systems

Excessive heat significantly elevates incidents of heart, lung, and kidney ailments and puts immense pressure on energy grids, hospitals, and essential infrastructure. Since March, Mexico has reported at least 125 heat-related fatalities and countless cases of heatstroke, with temperatures hitting an unprecedented 52°C on June 13, marking the hottest June day in its history.

The intense heat waves have aggravated drought conditions, worsened air quality, caused blackouts and water scarcity, triggered thousands of wildfires, and led to mass mortality among endangered wildlife species. The full toll of illness and death caused by the heatwave remains uncertain due to delayed reporting and unconfirmed cases.

Phoenix, Arizona—the hottest major U.S. city—has faced severe impacts. By June 8, medical examiners in Maricopa County were investigating 72 suspected heat-related deaths, an 18% rise from last year. Over 34 million people across the American Southwest were on heat alerts, with numerous heat exhaustion incidents reported during public events. Eighty-two-year-old Margarita Salazar Perez from Veracruz highlighted the harsh reality, saying, “It’s an oven here. You can’t stay here,” exemplifying the plight of those without adequate cooling.

Climate Change’s Role in Amplifying Heatwaves

To assess how human-induced warming influenced the recent intense heat episodes in North and Central America, WWA’s international team reviewed meteorological records and climate modeling data. Using robust, peer-reviewed techniques, they compared the current climate, warmed by approximately 1.2°C since pre-industrial times, to the cooler baseline of the past.

The analysis revealed that due to climate change, daytime temperatures during the heatwave were about 1.4°C higher and the event itself 35 times more frequent than historical norms. Nighttime heat impacts were found to be even more severe, with temperatures elevated by about 1.6°C and event likelihood increasing by a staggering 200 times—posing heightened health risks as recovery is hindered without cool nighttime temperatures.

WWA’s findings underscore urgent changes in heatwave behaviors. Izidine Pinto, co-author and scientist at the Royal Netherlands Meteorological Institute, warned, “As long as fossil fuels keep being emitted, heat waves will worsen, claiming more lives and driving up living costs.”