Heat Dome Continues to Plague Millions, Relief Uncertain.

Millions of Americans are expected to suffer as a heat dome expands beyond Texas this week, with temperatures soaring to record levels above 110 degrees. As of Monday, more than 45 million Americans live where some level of heat alert is in effect, according to the National Weather Service. The heat dome, which occurs when a persistent region of high pressure traps heat over an area, is expected to expand north into the Plains and east into the Southeast, leading to dangerous heat index values and increasing the potential for heat-related illnesses.