Living here in Phoenix, I can't stand those humid, wet summers of Houston/Florida/etc. I'd take the 108 we get here always.

Since it looks like you already live in the Washington area, I'd say give PHX a try. Change of pace and a good starting location to see some of the west coast for short getaways. And you'll get used to the heat quickly enough. Then again, IAD is probably easier for you since you're already there.