A significant portion of the United States, impacting over 200 million people, is under heat alerts as sweltering temperatures are expected to persist. The eastern half of the country is particularly vulnerable, with heat indices potentially reaching a dangerous 120 degrees Fahrenheit. Residents are urged to take precautions against heat-related illnesses, including staying hydrated, seeking air-conditioned environments, and limiting outdoor activities during peak heat hours. Local authorities are issuing guidance and opening cooling centers to help mitigate the impact of the extreme heat.