"I figured it was cooler in the summer than here in the midwest..."
HAHAHAHAAHAHAHAHAHAAHAHAHAHAHAHAHAHAHAHAHA!
Up until building air conditioning became relative common, Washington, DC, was considered a TROPICAL posting for diplomats from most European nations.
The heat and humidity in DC metro during the summer can be absolutely grinding. It's almost something alive.
It's fairly rare for the thermometer temperature to go over 100 here, but it does happen.
But, it's VERY common for the "felt temperature" which is derived as a combination of the thermometer temperature and the humidity, to be 100+ for days, or even weeks, on end.
The highest I specifically remember was 112-115 in 1993 during a nearly 3 week heat wave that was just crushing.
My exwife and I chose to go to Mt. Vernon on July 2 or 3. BIG mistake.