Sweltering heat wave grips central and southern U.S. for a second straight day

At least 40 million people were under extreme heat warnings across central and southern parts of the United States on Sunday as high temperatures and severe humidity gripped large swaths of the country for a second straight day.

At least 40 million people were under extreme heat warnings across central and southern parts of the United States on Sunday as high temperatures and severe humidity gripped large swaths of the country for a second straight day.

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Heat indexes exceeding 105 degrees Fahrenheit stretched from Minnesota down to Mississippi, extending west into Southern California and Nevada. Parts of the Southwest could see highs of 120 degrees Fahrenheit on Sunday, according to the National Weather Service.

Meteorologists said the sweltering weather was the result of another heat dome — a phenomenon in which atmospheric conditions trap heat, accentuating and prolonging already high temperatures.