Extreme weather has increased the number of preventable deaths in Brazil and around the world.

A study published in May in the scientific journal Temperature reveals how extreme heat and cold have been killing people silently—and unevenly. Analyzing mortality data in India between 2001 and 2019, researchers found that more than 34,000 people died from causes directly linked to intense heat and cold. India was chosen as the study site because of its combination of vulnerabilities—high population density, poverty, uncontrolled urbanization, and accelerated climate change—characteristics that resonate in Brazil.

Beyond the absolute number of deaths, the research reveals an important pattern: working-age men were most affected by extreme heat, while deaths from cold were evenly distributed between genders. Mortality was particularly high in states with less urbanization and lower public social spending, suggesting that urban infrastructure and social protection can act as shields against temperature variations. The authors conclude that many of these deaths could have been prevented with appropriate strategies.

But the warning goes beyond India. Unlike other climate-related threats, such as floods or wildfires, the effects of intense temperatures are often silent. The World Health Organization (WHO) estimates that 489,000 people died from heat exposure worldwide between 2000 and 2019. In Europe, a region that, in theory, would be better able to protect itself, the 2003 heat wave was responsible for more than 70,000 deaths in three months.

Nurse Lis Leão, a senior researcher at the Albert Einstein Teaching and Research Center at Einstein Hospital Israelita and editor of the book "Nature, Climate, and Public Health" (2024), agrees with the study's authors that these deaths could be prevented with adequate conditions and public policies to reduce exposure to heat and cold. "But we know that not everyone has the opportunity to take precautions and be in a position to protect themselves from extreme temperatures," she reflects.

Extreme weather takes an uneven toll

Extreme temperatures have also impacted the health of the Brazilian population. A 2022 study published in the journal Nature Medicine , based on data from 326 cities in nine Latin American countries, reveals that approximately 6% of all urban deaths are associated with extreme heat and cold. The research shows that, on days of intense heat, each 1°C increase in ambient temperature was associated with an additional 5.7% of deaths overall, and that 10% of deaths from respiratory causes can be attributed to the cold.

Another study, published in December 2024 in Environmental Epidemiology , shows that Brazil recorded more than 142,000 deaths related to extreme temperatures between 1997 and 2018. Although the cold was responsible for the majority of these deaths (113,000) — especially in the South and Southeast regions —, the number of deaths associated with heat has been growing rapidly, especially in the North and Central-West regions.

The human body's thermal regulation system works well in mild temperatures. It is in extreme heat and cold that significant physiological changes begin. Excessive heat exposure can cause heat stroke, cardiac arrhythmia, heart attack, pulmonary edema, and vasodilation. It also increases the risk of acute renal failure, stroke, neurological disorders, and mental disorders. Severe cold, on the other hand, poses cardiovascular and respiratory risks and can increase the occurrence of infectious diseases, such as pneumonia.

All of this primarily affects the most vulnerable populations: the elderly, who often live alone and without care; and newborns, who have not yet developed the ability to regulate their temperature. But the risk also intensifies for those who live or work on the streets.

Data from the Institute of Applied Economic Research (IPEA) from 2022 indicate that Brazil has approximately 282,000 homeless people, many of whom are continually exposed to severe temperature fluctuations, lacking shelter or regular access to drinking water. Workers in construction, agriculture, waste collection, and other outdoor activities also face long hours in intense sun or cold—often without any specific protection.

For Leão, climate inequality is revealed in these situations. "Who is taking care of these workers or the homeless? We depend on public policies that consider these climate changes to better serve this type of population," he states.

This gap appears in educational initiatives, often designed without considering the real conditions of those who need them most. "Health education is very important, but we can't lose sight of the population we're targeting," warns the Einstein researcher. "For example, if I talk about avoiding sun exposure during the hottest hours, between 10 a.m. and 4 p.m., those who work outside don't have that option. What other measures can we implement?"

She cites specific initiatives that attempt to mitigate risks, such as adapting construction work schedules or encouraging continued hydration among the elderly, who are more vulnerable to dehydration. But these actions remain isolated given the increasing frequency and intensity of extreme weather. For the researcher, the response must be structural. "We need public policies that can improve people's lives so they can face these heat and cold crises, which will become increasingly frequent," she says.

Lack of investment and resources

With scientific evidence and real tragedies mounting, the current Brazilian government administration has resumed its agenda of finding solutions. In 2023, the federal government launched the Climate Plan, an interministerial strategy that guides public policies for mitigating and adapting to climate change through 2035.

As part of this agenda, the Ministry of Health established the Health Sector Plan for Climate Change Mitigation and Adaptation, recognizing the direct effects of climate change on the population's health and proposing guidelines for addressing these risks. Meanwhile, at the Ministry of Cities, projects focused on resilient green cities and peripheries seek to support vulnerable municipalities with interventions such as urban greening and cooling centers.

According to Diego Ricardo Xavier, a researcher at the Institute of Scientific and Technological Communication and Information in Health at the Oswaldo Cruz Foundation (Icict/Fiocruz), there is also an effort to strengthen epidemiological surveillance based on the integration of environmental data and closer ties with institutions such as the National Institute of Meteorology (Inmet) and the National Institute for Space Research (Inpe), which produce essential information for the development of warning and monitoring systems for extreme events.

At the local level, São Paulo maintains Operation High Temperatures, with hydration tents for homeless people during the hottest days. In Rio de Janeiro, the death of a young woman at a concert amid the 2023 heat wave exposed the lack of measures to address extreme temperatures. Following the incident, the city instituted a protocol in 2024 that defines heat levels on a scale of 1 to 5. In February 2025, Rio recorded level 4 (prolonged extreme heat, between 40° and 44°C) for the first time, prompting authorities to issue public health alerts and guidelines and to establish a special program in health facilities to treat cases of hyperthermia.

In the southern states, emergency cold weather measures are being implemented more frequently: temporary shelters, coat drives, blanket distribution, and hot meals are becoming part of the winter calendar in cities like Curitiba, Porto Alegre, and Florianópolis—although with limited capacity in the face of growing demand.

Despite these initiatives, Leão considers that efforts are still far from forming an integrated and effective response. Part of this difficulty lies in the very way climate is perceived: as an external, diffuse, and poorly measurable variable. "In fact, not even the other social determinants of health, which we've known about for much longer, are adequately addressed, such as basic sanitation and access to healthcare itself. Problems that have been known for longer are still not adequately resolved," he observes.

For the Fiocruz researcher, there's still a lack of coordination between ministries, as the impacts of climate change on health are just the tip of the iceberg of a problem that begins much earlier, in production, consumption, and economic development models. "It's a cross-cutting and quite complex process. We need interventions that consider a change in culture, education, and the economic model," he states.

In the Einstein researcher's view, priority measures include developing adaptation plans focused on health, accessible early warning systems, cooling and hydration centers, urban greening, professional training, and specific protocols for addressing the effects of heat stress. But the main obstacle is putting investment in these areas on the agenda.

"Adaptation plans require intersectoral coordination. They require investment. At the COP [ United Nations Climate Change Conference ] itself, health is still a topic with very few resources. Money is being invested in other climate-related areas, such as energy transition and transportation, and not in health, which is the ultimate target of climate change," says Leão.

Even with the growing public awareness that the climate is changing—and directly affecting health—the response is slow. "We need greater agility to design these adaptation plans, implement them, and then evaluate whether they've worked. But we haven't even designed them all yet, let alone implemented and evaluated them," summarizes Leão.

Source: Einstein Agency

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