An excessive heat warning is in effect for heat indexes up to 105 to 110.
Source
The Washington Post
D.C.-area forecast: Oppressively hot today and tomorrow, with triple digit highs
15
Jul
Jul
.. . . . . . . . . . . . . . . . . . . . . . . . . %%%. . . * . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ - - - - - - - - - - - - - - - - - - - - . . . . .