I would think that for most paphs, the issue would be one of blooming, rather than survival. In other words, assuming that temps are say, in the 90's, and air movement is OK and the proper amount of water is available, the plants should survive, and maybe grow OK, but may not initiate buds. Here in NYC, heat waves occur regularly in summer. My cool growing paphs, all outdoors, including parvi's, insigne-types, complex hybrids, all make it through the summer without problems. Blooms are another story. Very rare is the paph bud that actually blooms in summer. Many buds get set in August, but don't always make it to blooming. (Actually, its the transition to indoor conditions that blast most late summer and early fall buds..they do fine as long as they can remain outdoors). I think you can still grow any type of paph. But for blooming, stick to warmer growers...but, hey...you may be able to have far more luck blooming multifloral paphs like philipinense than I ever will!