Heat wave across U.S. raises health risks and economic costs

The heat wave that blanketed much of the United States over the Fourth of July weekend put tens of millions of people under stress and pushed power systems hard enough to threaten thousands of homes. Its costs went beyond discomfort and blackouts, showing up in lost work hours, higher electricity bills and slower business activity as extreme temperatures spread across the country.

Justin Mankin, a Dartmouth professor who studies climate and economics, has said extreme heat carries economic consequences and that the effects are negative in almost every case. That damage is often hardest to see in the moment. Outdoor workers lose productivity, shoppers stay inside, companies sell less, and regions hit by the worst temperatures see output fall as cooling demand rises.

The longer-term trend is just as stark. The Fifth National Climate Assessment, the federal government’s leading climate report, said in 2023 that the average number of heat waves in 50 large U.S. cities has doubled since the 1980s. Related materials from the assessment also show the average heat-wave season in those cities stretching from about 40 days to about 70 days, turning what used to be shorter bursts of extreme weather into a much longer economic drain.

The public-health toll has risen alongside the financial one. Centers for Disease Control and Prevention surveillance found annual U.S. deaths involving excessive natural heat ranged from 297 in 2004 to 1,153 in 2020. The CDC now tracks heat-related emergency department visits, hospital stays and deaths through its Heat & Health Tracker and related tools, reflecting how often the hazard now turns into a medical emergency.

The economic damage reaches well beyond utility bills. National Oceanic and Atmospheric Administration materials say heat can damage power lines, buckle roads, reduce classroom learning, lower labor productivity and add direct health-care costs. A Duke University Nicholas Institute report covering 2001 through 2023 estimated U.S. heat-related productivity losses at more than $90 billion a year in some estimates. Separately, the National Safety Council said 48 workers died from exposure to environmental heat in 2024, underscoring the danger for construction crews, farmworkers and other people who cannot escape the sun.

Together, those figures point to a national reality that is changing fast: heat is no longer just a weather event. It is a recurring economic shock that hits household budgets, workplace safety, retail sales, agriculture and the power grid at the same time.