From CNN:
An expansive and exceptionally strong heat dome builds Sunday over the East and expands to reach the Midwest and Great Lakes over the following days, ushering in the regions’ first significant heat wave of the year. Heat domes trap air in place and bake it with abundant sunshine for days on end, making each day hotter than the last.
This one will make temperatures skyrocket to levels hotter than even the hottest typical summer day. Hundreds of temperature records could fall by the end of next week, both during the day and at night.