How to stay cool in the summertime:
1. Eat spicy foods. It has to be spicy enough to make you sweat, so that after you finish, the temperature around you then feels cool.
2. Tell scary stories. This will cause you to have goosebumps and shiver, thereby making you feel cool.
3. Go to an onsen (which is bascically an outdoor hot tub). Stay in just long enough to make you warmer than the outside air temperature. Then, when you come out you will feel cool.
4. Eat shaved ice.
5. Leave the area. Travel north where the temperature is cooler.
These are the preferred methods for staying cool in Tokyo (or not in Tokyo, as is the case in number 5). Hope you're staying cool where you are!
Now, please excuse me, it's time for me to go find some curry.