I had been there many times but it was my first time travelling in summer, and I LOVED IT!!
I had often visited there in autumn because Kyoto is famous for it's beauty of colored leaves. But as so many people think the same way, the place gets very very crowded.
In summer, on the other hand, the place is nice and quiet.
You can spend hours looking at gardens of temples.
Below left is Eikando and right is Nanzenji.
In July, the famous festival called Gion Matsuri is held in Kyoto. The highlight of the festival was over (on the 16th and 17th), but when I went there on the 24th, there was Hanagasa junko parade.
If you ever visit Kyoto, I strongly recommend you to go in summer! (That is if you could put up with the heat.)