July and August are very hot. We went the first week in June this year and apart from one thunderstorm, that only lasted a couple of hours, the weather was lovely, warm enough to sunbathe comfortably.
It depends what you enjoy doing on holiday, if you enjoy swimming July or august may suit you. Whenever you go you will love Corfu. If you want somewhere quieter head for the west coast where they have sandy beaches. The north east coast above Corfu town is lovely, though the small cove type beaches tend to be pebbley. Ipsos is for the young party people imo, and Benitses had a similar reputation