WASHINGTON – A widespread high-pressure system, known as a heat dome, is set to bring scorching temperatures to the northern United States just as summer officially begins. Millions of people in the northern tier are under heat alerts as this system moves eastward, impacting major cities like Chicago, Detroit, and those along the East Coast corridor. The heat wave is expected to peak from Sunday through Thursday, with temperatures soaring well above average and heat indices reaching dangerous levels. Heat advisories have already been issued for various regions, warning residents about the health risks associated with prolonged exposure to extreme heat. Vulnerable populations, including children, the elderly, and outdoor workers, are especially at risk during heat waves. Cooling centers are being made available in communities with heat response plans to help residents stay safe. While temperatures are forecast to return to normal levels by early July, the hottest days of the season typically occur in mid to late July.