The Cost of Extreme Heat Is Displacement

Extreme Heat Linked to Migration Through Economic and Health Pressures

This summer, record temperatures across Europe and the United States have prompted millions to seek relief through public pools, libraries converted into cooling centers, and increased air conditioning use where available. Some have traveled to higher elevations or coastal areas, though many of those locations have also recorded heat advisories. Early analyses of Europe’s June heatwave estimate at least 20,000 deaths. For many residents, these conditions remain seasonal. For others, sustained high temperatures contribute to longer-term decisions about relocation.

Researchers have defined a “human climate niche” as the historical range of rainfall, humidity, and temperatures associated with human settlement patterns over millennia. A study published in the Proceedings of the National Academy of Sciences projects that, under continued high greenhouse gas emissions, up to one-third of the global population could live outside this range by 2070. Sustained wet-bulb temperatures at or above 35°C (95°F) have been identified as a threshold at which the human body cannot cool itself through perspiration. Several cities have recorded readings at or near this level. Before regions reach physiological limits, heat affects agricultural output, labor capacity, and household finances.

Movement linked to heat typically occurs alongside other pressures rather than from temperature alone. Households with greater resources can install cooling systems, pay higher energy costs, or relocate temporarily. Communities with larger budgets can fund infrastructure such as shaded public spaces and early-warning systems. In lower-resource settings, repeated heat exposure compounds losses in income and health. Crop yields decline after successive heat events. Livestock mortality rises. Outdoor workers in construction, vending, and farming face reduced hours or lost wages. Expenditures on water, food, electricity, and medical care increase while earnings fall. Pregnant individuals encounter elevated risks of adverse birth outcomes. Children experience interruptions in schooling when facilities close. Older adults face higher rates of heat-related illness. Nights without sufficient cooling prevent physical recovery.

Migration results from cumulative effects over multiple seasons. Santuben Kantibhai, a farmer in Gujarat, India, experienced successive heat events that reduced crop yields and family income. Her father, who contributed through farm and wage labor, developed cataracts that limited his ability to work. A subsequent heatwave further lowered production at the time medical costs for surgery arose. Parametric insurance provided a payout that covered part of those expenses and supported continued farm operations.

Cooling measures such as tree planting, reflective roofing, shaded streets, and improved building design can lower local temperatures by several degrees. Early-warning systems have reduced mortality in implemented areas. Financial instruments including parametric insurance have transferred income risk during extreme events. The World Bank Groundswell report estimates that, under a high-emissions pathway, up to 216 million people could move internally within their countries by 2050 due to climate-related factors. The same report states that ambitious adaptation measures combined with emissions reductions could lower that projection by as much as 80 percent.

Exposure and response capacity differ across populations. Factors including income, gender, age, disability, and legal status correlate with varying levels of heat risk and access to support. Some analyses estimate that women represent approximately 80 percent of people displaced in connection with climate-related events; the basis and methodology for this figure are not uniformly documented across sources. Women and girls frequently perform unpaid tasks such as water collection and caregiving that continue during high temperatures. Cultural norms regarding clothing and mobility can add to exposure in certain settings. Adaptation programs that do not account for these differences may reach some groups less effectively.

Individuals who relocate may encounter heat during transit or at destinations. Routes through arid regions such as the Sonoran Desert have recorded high temperatures. Migrants entering urban labor markets often work in outdoor sectors with elevated heat exposure. In 2021, Sebastian Perez, a farmworker from Guatemala, died during Oregon’s heatwave when temperatures reached 107°F (42°C). Heat-related occupational risks apply regardless of origin.

The World Bank analysis models internal movements only and emphasizes that policy choices on adaptation and emissions directly influence projected numbers. Measures already identified include urban greening, worker protection standards, livelihood support, and reductions in fossil fuel use. Implementation depends on available domestic and international financing. The report indicates that earlier and larger-scale action correlates with lower displacement figures under modeled scenarios.