This summer, as record-breaking heat sweeps across Europe and the United States, millions of people are searching for a way to cool off. They crowd into public pools, and libraries turned into cooling centers. They run their air conditioners around the clock—if they have them. They flee to the mountains or the coast for relief, only to find that many of those traditional escapes are under heat advisories.
For many, the very real dangers of extreme heat (early analyses of Europe’s June heatwave estimate a death toll of at least 20,000) will pass with the season. But for millions of others, heat is not just something to survive for a few weeks. It has become a reason to leave home altogether.
Scientists have identified a “human climate niche”—the range of rainfall, humidity, and temperatures in which human societies have thrived for thousands of years. Climate change is rapidly shrinking that niche.
By 2070, up to one-third of humanity could be living outside these conditions most suitable for human survival if greenhouse gas emissions continue unabated, according to a study published in Proceedings of the National Academy of Sciences. Extreme heat is central to that shift. Scientists have long warned that sustained wet-bulb temperatures of 35°C (95°F) or more—when heat and humidity combine to prevent the human body from cooling itself—are not survivable. Several cities have already breached this threshold, and emerging evidence suggests the body’s breaking point may be even lower. Long before entire regions become physiologically uninhabitable, however, they become economically, socially, and practically impossible to live in.
People rarely move because of heat alone. They move because heat makes it too costly to stay. Whether someone can remain in place increasingly depends on whether they can afford to adapt. Extreme heat is not just a climate hazard, it is a force multiplier for inequality. Wealthier households can cool their homes, absorb higher utility bills, and relocate temporarily during heat waves. Wealthier cities can invest in solutions to keep cool. However, billions of people around the globe have no such options. For them, each hotter year brings a new set of compounding losses.
Crops fail after repeated heat waves. Livestock die. Construction workers, street vendors, and farmers lose income as dangerous temperatures shorten working hours or make outdoor labor impossible. Families spend more on water, food, electricity, and healthcare while earning less than before. Pregnant women face higher risks of miscarriage and preterm birth. Children suffer heat-related illness and education losses as schools shut down. Older adults become increasingly vulnerable. And when scorching days are followed by nights that never cool, the body doesn’t have a chance to recover.
Migration is rarely the result of a single heat wave. It is the culmination of years of mounting losses that steadily erode income, health, and hope.
Consider Santuben Kantibhai, a farmer from Gujarat, India. Over the past two years, her family has endured a cascade of climate and economic shocks. A severe heatwave destroyed much of their standing crop, causing her family’s income to plummet. At the same time, her father—a co-earner who relied on farm labor and daily wage work—developed cataracts that gradually robbed him of his eyesight, making it increasingly difficult for him to help their family earn a living. When another heatwave struck in 2025, crop yields fell again just as his condition required surgery. For Santuben, the question is not whether heat is becoming more dangerous; she already knows it is. It is how many more failed harvests and lost workdays can her family absorb before staying becomes impossible.
The encouraging news is that we are far from powerless. We already know many of the solutions. Trees can cool neighborhoods by several degrees. Cool roofs, shaded streets, and passive building design reduce dangerous temperatures. Early warning systems save lives. For Santuben, financial tools—in her case, parametric insurance—cushioned income losses during extreme heat and allowed her to cover her father’s medical expenses, which enabled him to return to work and recoup some of the income heat had wiped out. The value of that support extended beyond protecting her family’s income, it helped preserve their ability to decide whether to remain on their land rather than being forced to leave because they had exhausted every other option.
The challenge is not a lack of solutions but a lack of resources. The communities most exposed to extreme heat are often those least able to finance adaptation, making increased domestic investment and international climate finance essential. None of these measures replace the urgent need to reduce greenhouse gas emissions, nor can they fully erase the pressures heat puts on families, but together they can often give people the choice to stay.
To succeed, however, solutions must also reflect that heat does not affect everyone equally. Just as economic status can impact whether someone is forced from their homes, so too can social factors, including gender, race, disability, and legal status, which often intersect to increase exposure to heat risks and reduce access to support systems.
Women, for instance, already account for an estimated 80% of people displaced by climate change and are significantly more likely to die during climate-related hazards. Women and girls often bear a disproportionate burden because they are more likely to shoulder unpaid caregiving, water collection, and cooking—responsibilities that continue even during dangerous heat. Cultural expectations around clothing and freedom of movement within a community can further increase their exposure. Adaptation strategies that ignore these realities risk leaving the most vulnerable behind.
Even when people leave home to escape the impacts of extreme heat, they may remain dangerously exposed. Many migrants face lethal temperatures on the journey itself, whether moving within a country from rural to urban areas where livelihoods are not as dependent on temperature, or crossing the Sonoran Desert or other increasingly hostile routes across borders.
Others arrive only to find themselves working in some of the hottest and most dangerous occupations. In 2021, Sebastian Perez, an undocumented farmworker from Guatemala, died after working outdoors during Oregon’s record-breaking heat wave when temperatures soared to 107°F and the asphalt softened beneath workers' feet. Heat followed him across borders.
Migration has always been part of the human story. But people should not be forced to abandon their homes, livelihoods, cultures, and communities because heat has become impossible to endure.
The World Bank estimates that, under a high-emissions scenario, as many as 216 million people could be internally displaced by climate impacts in the next quarter century. But it also finds that ambitious adaptation and emissions reductions could cut that number by as much as 80%. When people leave because climate impacts force them out, migration is not adaptation. It is evidence that adaptation came too late.
We already know how to reduce the risks of extreme heat. We know how to build cooler cities, protect workers, strengthen livelihoods, and cut the fossil fuel consumption driving temperatures ever higher. What has been missing is not knowledge, but political will. If we fail to act, the question will no longer be where we go to escape the heat. It will be whether any place remains beyond its reach.
