Is it very hot or acceptable?
It's very hot (summer) in Mecca now a days. The maximum temperature is around 45C (45-30 C daily range) so you need to have light colored/white, cotton clothes.
It is very hot in June
Hot but acceptable if you are in the Harraam. It's around 40C (100F).
Very, very hot and humid. Drink lots and lots of water, and make sure that you take your sanitizers to avoid Coronavirus infection in crowded places like the Masjid al-Haram.