"Will summer be too hot...?"

Not for me it won't. It may get a bit too humid at times, but never too hot. I've spent a few August weeks in inland Andalucía (quite near Tabernas Desert) when the temperature is routinely in the range 35 to 40C, similarly in Granada and Córdoba, with humidity in the teens or single numbers. I can take that any time with the proviso that my balding head and my forehead mustn't be allowed to burn. On the other hand, we were at Lake Como one June in temperatures of 35 to 37C in high humidity. Foolishly, we decided to do the steep uphill hike to Chiesa San Martino, a tiny church perched high on the mountainside above the lake. We thought it would be OK because much of the hike was in the shade of woodland. We forgot that the trees also cancelled out the breeze completely. Fortunately for us, we were the only eejits daft enough to try the climb that day and we were able to eat lunch disrobed with clothes spread out to dry on the rocks. What a view though (of the lake and mountains, not us). A terrific overnight thunderstorm cleared the air. Next morning the mountains were draped in wisps of cloud with the peaks standing proud in the sunshine.

So I don't agree with the Bard when he writes that "Sometime too hot the eye of heaven shines," but I'm with him when he says that "...summer's lease hath all too short a date."