Nearly 250M people in America's Midwest, northeast brace for heat wave

A heat wave currently roasting the southeastern US is expected to spread into the country's Midwest and northeast, potentially affecting nearly 250 million people, the National Weather Service (NWS) said on Saturday.

According to the NWS, temperatures will remain at 32 degrees Celsius (90F) or higher for at least a week, possibly extending until June 26.

"The first heat wave of the summer begins Sunday over the middle of the nation, before spreading to the Midwest and to the northeast by Tuesday then lasting most of next week," the weather office said.

Temperatures could reach up to 40.56C (105F) in some areas, setting new records and leading to very warm nights.

Major cities such as Chicago, Indianapolis, Cleveland, Pittsburgh, Philadelphia, and Boston are expected to experience their hottest days of the year, accompanied by high humidity levels.

The southeast has been experiencing a heat dome, where high-pressure systems trap hot air, preventing cooler air from moving in and inhibiting cloud formation.