Hi,
We're not wusses, but we recall being on a 2nd floor in London, on the 5th floor of a mountain resort on Colorado and on the third floor of a hotel on the Isle of Skye, Scotland where it was really so hot at night in June/July that we had a hard time getting to sleep. It made the following vacation day less fun, (because we were over-tired and less fun). We've stayed in other places where maybe it was a little warmer than usual, but not really a big deal in terms of comfort/sleep.
Do Rick Steves tours usually stay on upper floors? How warm are rooms with "no or weak air conditioning"? Any feedback on having difficulty getting to sleep with only a sheet or not sheet covering you?