I don't know where you get your information but it does get cold in parts of Egypt to the point of ice. For instance mount Catherine

https://en.m.wikipedia.org/wiki/Mount_Catherine

All though extremely rare in it does snow in Egypt from time to time. So I believe yes some but not all of ancient Egyptians new what ice was.

A better location to pose this question might be somewhere equatorial, such as Singapore. Apologies for not actually answering your question, but the lowest recorded temperature in Singapore was 19.4 °C (66.9 °F) in January 1934.

Cairo is at 30 degrees north latitude -- a latitude shared by US states like Florida and Texas. Both warm, but definitely can have ice (and even snow) on rare occasions.