There will be three, four, maybe five days in a row of a persistent heat dome with hot, humid, sunny conditions over a good portion of the Eastern U.S.,” said Bryan Jackson,

Summer will make a dramatic entrance in the U.S. this week with a heat dome that will bring stifling heat and uncomfortable humidity to millions.

Major cities across the United States are preparing for extreme temperatures caused by a heat dome that hit the U.S. Plains on Friday and is expected to expand to much of the rest of the country over the coming days.