And so it comes…. how can someone feel cool in Athens during hot Greek summer??
Day Tips are: find a good airconditioning cafe for the day.
If you want to walk, always keep a bottle of cold water (they sell it everywhere and it is very cheap)
Try to go to seaside, either south Athens or eastern Athens and combine with your trip a visit to archaeological sites there (so as not to lose you day without learning something new).
Try to visit a tavern next to the sea.
You can also visit Piraeus and Mikrolimano that is near the sea.
Night tips are: most of the clubs use aircoditioning. Before that, you can visit an Open Air Cinema, there are many in Athens.
Drink cocktails, most of the bars know their task, that is to refresh people.
Generally at night temperature gets lower, and if you combine it with a visit either to a hill or to a close-to-the-sea-nightclub, that would be perfect.
General tips: eat more fruits and raw vegetables.