Hey Chip,
I was last November there and the sea was toasty warm (26-28, like in Cayman last Jan) but the year before when I also went, it was a few degrees cooler (23°C). Air temp can vary a lot but note that it is often very windy. I'd bring a sweater and a shell jacket.
Cairo will be materially warmer. Do visit the coptic area, and if you do the pyramids, don't buy the ticket to go in; not worth it! If you have several days to spare, try the Black and White Desert and bring a mini tripod, you'll get fantastic pictures of the sky at night (milky way) and the desert!
Hope all is well!
Alex