Hi Hilarylb,
August is supposed to be one of the hottest months in Egypt but don't let that put you off. Your tour guide will be knowledgeable in the weather conditions at this particular time and will ensure to everyones comfort and safety. Just take plenty of High Factor SunTan and PreTan lotion and a good pair of sunglasses, drink plenty of water and be sensible and I'm sure you will have a wonderful time.
I did the Pyramids and Nile Cruise last October and had a wonderful time. It was pretty warm then but then again living on the North East Coast anything over 12 Degrees Centigrade is hot.