Overnight and early morning temperatures never went down making cooling off in the extreme heat much more difficult.
Heat, haze and humidity - with plenty of sunshine - is in store for Monday. There is risk of an isolated thunderstorm in the metro area.
A hot week is ahead with temperatures in the high 80s and 90s through the weekend.
The heat index is expected to climb to 102 in D.C. Monday.
Residents are urged to stay in air-conditioned buildings, to take advantage of cooling centers and spray parks, and to check on the elderly.