We were in Corfu last August (2nd and 3rd weeks), daily temperature was in excess of 32 degrees every day with hardly any cloud. Night temperatures were comfortable. We made sure our air con was running continuously. Only had 1 bad day when the wind got up temp was still about 28 degrees thogh !!!
Stayed in Roda at the Roda Beach Village - great place something for everyone. There were 10 in our party 4 adults and 6 kids.
Corfu does get a lot of Italian visitors during this time, who can be loud shall we say.
Waterpark is a good day out - but book through theagents in town, a lot cheaper than the tour company.
Have a good time, Corfu is a wonderful place and the people are ever so friendly.
Hop this has been of use to you.