There are some freestone streams in my region (Lancaster/York county) that are fish able right now. I personally temped them out at 65 degrees in the afternoon. I'm fishing bass right now because it's simply produces better results this time of year, however I could be ethically fishing them if I wanted to. Each stream is different and its best to carry a thermometer and have a plan B Or C if things don't work out.
The Bushkill in Easton is a spring influenced stream which gets the majority of the flow from a quarry discharge. Temperatures and water levels are likely more stable but it does bake in the daylight and I would expect temps over 70 degrees during the day at some point.
Bottom line, you don't have to rule out summer trout fishing, just be smart and have a good plan.