If you are planning a trip to Greece this summer, it will be worth your time to skim this article:
https://www.cnn.com/2025/05/28/travel/athens-heat-greece-tourism-summer
It has been several years since we visited Greece (I think it was in September), but I remember arriving at the Acropolis, thinking we would make the climb, but changed our minds when a physically fit young lady from New Zealand was in the restroom wringing out her shirt (from sweat), having just finished coming down from the Acropolis. We opted to go into the lovely glass-floored museum (with a decent view) instead.
Perhaps, consider cooler months.