Millions of Americans are facing oppressive heat, with forecasters expecting a "heat dome" to develop over parts of the county over the weekend and through next week. The National Weather Service (NWS) warns that heat related illnesses increase significantly during extreme heat events.

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

A few locations could approach or top 100 degrees, including Denver, which happens only twice a year on average, said Weather.com meteorologist Jonathan Erdman, who added that "New York City and Philadelphia could also flirt with the century mark during the peak of the heat wave next week.