Why worry about Penns Creek because there is nothing to worry about? I live pretty close to Penns (same general area, at least) and the weather, temps, level of rainfall, etc hasn't been bad at all. Overall, this summer has not been all that hot compared to other years in the not-so-distant past. There is no sense in being overly concerned about things that you cannot control. The trout in Penns Creek will be fine. Actually, we have just crossed the slope of temperature trends where average temperatures start to fall as we head closer to autumn. Sure, it seems a long way off, but the cooling trend is now beginning. That doesn't mean the end of heat-waves etc for the year, but the trout have pulled through worse.
Also, Penns is posted with stream temperature signs reminding anglers about taking this into consideration. Also, the catch-rate when stream temps are high is so much lower that a person fishing under ideal conditions probably kills more trout due to catch and release than someone fishing right now would. More trout and more trout handled means more chancing of death for each and every fish. You go out now and catch two they both might die, sure. You go out and catch fifty in May and more than 2 could easily die, so...... A lot of people still overhandle fish, hold them out of the water longer than necessary, and do other stupid stuff with the fragile trout.
Just my opinion, but I am sure that Penns will still be loaded with trout come next spring. well