I have been to Egypt three times, in July, December and January.
My last visit was in January 2023. My wife had never been to Egypt and I was a bit surprised that the weather was cooler than I found it in December 1985. It actually snowed in northern Egypt while we were there.
Daytime temps ran largely in the 70s perhaps up to low 80s, but nighttime dipped in the 50s. Some of our five star hotels didn't have heat. Thankfully, I brought my leather jacket, but wished I had brought a sweater.
When I was there in 1985, temps were as high as the 90s and it was never chilly.
Definitely don't go in the Summer.
We went during prime tourist season and the country is loaded with tourist, but our tour guide was great and we managed quite well. Our Gate 1 tour was well organized and frequently we took an early start in the morning to get ahead of the crowds. The most crowded places we visited were in Cairo, where the traffic is terrible. Even the pyramids at Giza was not a problem, despite all the tourists.