The American Red Cross has some tips on how to beat the summer heat.
Drink lots of water, so that you stay hydrated.
Take it easy, if you are working or playing outside take lots of breaks and get out of the heat.
Dress for the heat, by wearing lightweight and light-colored clothing
Know the signs of heat stroke so that you know when to seek medical attention
Also don't forget your pets, make sure they have shade, plenty of water and don't leave them in the car.