Alright, so your ears might not fall off from not wearing a hat. Especially in Cairo, where the average year long temperature is a comfortable 72 degrees Fahrenheit (22 degrees Celsius). Of course, depending on what time of year you travel, the temperature can be extremely different. For instance, visitors stopping by during the summer months (June to August) can expect to find temperatures around 95 degrees Fahrenheit (35 degrees Celsius). If you're more for the colder temperatures, then go to Cairo in the winter months (December to February), where the temperature will bottom out around 48 degrees Fahrenheit (14.5 degrees Celsius).
You probably haven't seen pictures of the world famous pyramids surrounded by lush vegetation and tropical fruit sprouting up everywhere. That's because through the duration of the year, Cairo only receives one inch (26mm) of rain fall. In fact there is only on average one day per month which sees any sort of precipitation at all. So I think you'll be safe to leave your umbrella and rain boots at home.
Bring your sunscreen because there is going to be sunshine. A lot of it. A typical day has nine and a half hours of sunshine, with June topping off at close to twelve hours a day. December, on the other hand, has only about six and a half hours of daylight.
If you've lived in Cairo your entire life you've probably never seen frost before. And why would you when the town averages a whopping zero days with frost. I guess you won't be needing your extra long johns or heavy wool socks for this trip either.
Outside of sunscreen (and plenty of it), you will need light weight, loose fitting clothing. Preferably articles that will cover more of your skin (unless you're going for that ultra bronze tan). Linen and light weight cotton are great, especially if they are long sleeved. Clothes made in these particular fabrics will allow your skin to breath better and keep yourself from overheating. Of course no matter what you wear, make sure to drink plenty of water. Keeping hydrated is far more important than any type of clothing you could wear.
