Heat dome grips central US, raising deadly heat risks

On July 24, Climate Central forecast Climate Shift Index levels of 5, the highest possible, across large areas of the United States through the heat wave as human-caused climate change fueled dangerous heat across much of the country. The heat dome spread from the western U.S. into the Midwest and South, leaving the central United States under dangerous temperature and humidity combinations that can turn life-threatening. Older adults, children, outdoor workers and people without reliable air conditioning faced the greatest risk as the heat settled in for days.

Heat can trigger dehydration and heatstroke, push electric demand higher as air conditioners run nonstop, and strain power grids just as hospitals and emergency rooms absorb more heat-related visits. Schools, sports programs and public events often have to shorten hours or shut down when indoor cooling cannot keep pace, adding pressure on families, employers and local governments.

Cities can be hotter than the surrounding countryside because pavement and buildings hold heat, creating urban heat islands. Rural areas are not safe by default, especially where farmworkers, delivery crews and construction crews spend hours outside and shade or cooling is limited. Active Heat Alerts, clear public communication, urban heat island awareness, heat action planning and tabletop exercises help communities rehearse responses before a wave arrives.

On June 20, 2025, Climate Central forecast a dangerous early-season heat wave would hit the central and eastern U.S. between June 20 and 24. At night, temperatures stay high after sunset, when bodies, grids and hospitals finally need relief.