Too hot? Too crowded? What to see in 2-3 days? Thanks
Go to this site to find actual daily weather data for any city for the last few years. Crowded - probably. Tons to see, depends on what your interests are and how well you hold up if it's uncomfortably hot for you.
Be aware, the weekend of June 15th there is a huge music festival going on and hotel rooms are at a premium.