Hospitalisations for heat-related illnesses in the United States could double over the next 15 years, new research warns, as rising temperatures driven by climate change collide with deepening economic inequality and a patchwork of unprepared public health systems.
The study, published in the American Geophysical Union journal GeoHealth, estimates that the annual number of heat-related emergency department visits or hospitalisations across the country will rise from approximately 109,000 cases today to as many as 237,000 by 2040. That projected surge would nearly double annual healthcare costs for heat-related conditions to more than $1bn, according to the research conducted by Vivek Shandas, a professor at Portland State University, and Stephan Brown of CAPA Strategies.
Severe heat already kills more Americans each year than all other extreme weather events combined, with heat-related fatalities increasing by more than 50 per cent between 2000 and 2025. In 2022 alone, 1,714 heat-related deaths were recorded. The authors warn that the coming years will bring a “sustained increase” in illness and death, not a plateau. “There is this staggering cost to society we are going to see over the next 15 years,” Shandas said. “Heat is an amplifying event – if you are already struggling with a pre-existing condition, there’s a good chance it will lead to some sort of illness like heatstroke or even death.”
Economic pressures and policy decisions deepen the crisis
While the elderly and those with existing health conditions are most vulnerable, the study and supplementary data make clear that economic factors and government policy choices are sharply exacerbating the health risks. The cost of keeping cool has become an affordability crisis: the average US household is expected to spend nearly $800 on electricity this summer, up more than 10 per cent from last year, according to a report from the National Energy Assistance Directors Association (NEADA) and the Center for Energy Poverty and Climate. The report’s authors warned that the rising bills will deter many from running air conditioning.
“When temperatures break records, utility bills often do too,” said Mark Wolfe, NEADA’s executive director. “For families already struggling to make ends meet, higher cooling costs can force difficult choices between paying utility bills and covering other necessities such as food, rent, or medicine.”
The affordability gap disproportionately affects poorer individuals who cannot afford air conditioning, work outdoors for prolonged hours, live in houses poorly designed for high temperatures, or have exacerbating health conditions. Low-income communities also face the urban heat island effect, where buildings, roads and infrastructure can add up to 20 degrees Fahrenheit to local temperatures. Racial and ethnic minorities, particularly those in neighbourhoods shaped by discriminatory development practices such as redlining, have less access to cooling resources and green spaces. A Harvard study has suggested that neighbourhoods with more green space see lower death rates during heatwaves.
Policy decisions at the federal level have compounded the problem. The administration of former President Donald Trump slashed programmes aimed at helping cities deal with extreme heat, and his tenure saw soaring energy costs for Americans. Meanwhile, extreme heat is not currently recognised as a “disaster” under the Stafford Act, the federal law governing disaster response, limiting the availability of federal assistance for heat-related emergencies.
The impact is far from uniform. The study projects that California and the Las Vegas area will experience the greatest total number of heat-related health problems, while regions less accustomed to extreme heat – such as the north-east and the Ohio Valley – are expected to suffer the most severe health consequences from each major heat event. Older adults are particularly at risk: over 80 per cent of US heat-related fatalities annually are adults over 60, and heat-related deaths in that age group increased by 88 per cent between 2018 and 2022 compared with the period from 2000 to 2004. Physiological changes with age, chronic conditions, and medications such as diuretics, sedatives, and some heart and blood pressure medicines can reduce the body’s ability to regulate temperature. Children, pregnant individuals, and outdoor workers – including farmworkers and construction workers – also face elevated risks.
Preparedness concerns mount as climate trends accelerate
The study examined 53 of the largest US metropolitan areas and projected outcomes under a range of greenhouse gas emissions scenarios against a backdrop of accelerating climate change. The US has already experienced its hottest March on record this year, with the summer expected to bring above-average temperatures and potentially widespread wildfires. Globally, the past ten years (2015–2024) were the hottest on record. The average rate of extreme heat events in US cities has jumped from two per year in the 1960s to ten per year between 2010 and 2020, and the average length of the heatwave season has increased by 46 days since the 1960s. By 2060, average temperatures in more than 240 major US cities are projected to rise by 3.6 degrees Fahrenheit. A 2019 study projected that the annual number of days with a heat index above 100°F nationwide will double, and days above 105°F will triple, by the end of the century.
Despite these trends, many cities – particularly in the northern latitudes of the US – remain “woefully unprepared” for extreme heat, Shandas said. A UCLA-led study found that while 78 per cent of large cities’ climate plans mentioned heat, few offered comprehensive strategies, and even fewer addressed the disproportionate impact on low-income residents and communities of colour. “We are seeing public health agencies under strain and a retracting of a lot of climate-related interventions across the country,” Shandas added. “I’m very concerned about this summer, particularly for older people on fixed incomes.”
The researchers stressed that heat-related deaths are likely significantly undercounted, as heat often contributes to fatalities officially attributed to other causes. Mental health conditions can also be aggravated during heatwaves, with research showing increased emergency room visits for mental health reasons. “It’s a moment where a number of trains are heading towards each other on the same track,” Shandas said. “The heat risk isn’t growing just because of the temperature – it’s growing because more vulnerable people are living in places that are getting more extreme heat.”