I have seen it reach 100 degrees when we had a warm summer several years ago. If it looks like I will have several days above 90 degrees, I bring the largest Pk inside with the A/C, because I have too many years invested in that plant and the flower is nice. I do leave the smaller ones in the greenhouse, but they are in a shadier location near the floor. My guess is that it is a few degrees cooler in that location. I do see stress in most of the phrags in the summer. It shows in the older leaves, but the new growths are OK. By the time they start to mature, summer is gone and cooler weather has returned. The greenhouse is not optimized for phrags. It's not really optimized for anything, but it is the best I can do for the money and effort I am willing to spend. MikeHow hot does your GH get? Is the PK in the GH?