Egypt is hot throughout the year. It is basically one big desert, it almost never rains (like 2 days a year), and the only thing you possibly have to worry about is a sandstorm.
The sun will be extremely intense no matter the season you travel. Expect temperatures starting from 30° Celsius / 86° Fahrenheit and way above.
The good news: It’s a dry kind of heat with an extremely low humidity so it won’t feel as hot as it actually is. Usually, it doesn’t cool off all that much during the night.
If you are visiting Egypt in winter (November, especially December & January, until March), you will be able to enjoy cooler temperatures around 10 to 25 ° Celsius / 50 to 77 ° Fahrenheit. The sky can be a bit overcast during that time of the year. But for visiting temples (Karnak / Luxor) or the Giza pyramids it might be the more enjoyable time of the year to travel.