Going back in time on satellite images it looks like the last day that had notable clouds during the day was Wednesday October 16. Basically wall to wall sunshine for the last 8 days.
Assuming the 99 at DCA is the high today, we will have a 14-day stretch with an average high of 97.2. That puts us behind only 1930 and 2011 as the hottest two-week stretch ever.
A solid 1.5 hours of 99’s on the five-minute obs at DCA. I know those get rounded multiple ways and are likely 98’s, but maybe we snagged a 100 somewhere in there.