I stayed at the Kaiserin Elisabeth a few years ago, during a late May heat wave, as it happens. I liked the hotel very much - it has a very sedate, old-fashioned but not stuffy air. Both rooms I occupied (a spacious double and then a ridiculous shoebox single) faced the inner courtyard and were very quiet except for the drunken woman yelling into her cellphone with her window open one night. I understand the streetside rooms can have some early morning traffic noise. The bathrooms were enormous, the breakfasts were splendid. All in all a nice place. Did not really feel I needed to turn on the AC, although I noticed the units on the wall.