Feels-like temperatures climbed to dangerous levels across the Midwest and East Coast as cities issued heat alerts, with water stations and cooling centers set up at fireworks and parade venues.

Health authorities urged the elderly and outdoor workers to avoid midday activity and to treat heat-illness symptoms as emergencies.

Grid operators went on alert for surging cooling demand, with some regions setting new summer peaks.

Meteorologists note heat waves are growing more frequent and intense each year, making urban heat adaptation a long-term task.

With heat also gripping Europe and East Asia this summer, cooling access and protection of vulnerable groups have become a shared policy theme across countries.