The food we eat can have a warming or cooling effect on the body. Foods that contain a high water content are generally considered cooling foods. Most fruits and vegetables fall into this category and can include:

Cucumbers
Tomatoes
Summer Squash
Zucchini
Bell Peppers
Eggplant
Lettuces
String Beans
Watermelon
Berries
Plums
Cherries
Nectarines
Peaches, etc.

Land animals on the other hand, have warming properties (beef, chicken, eggs, turkey, duck, buffalo), but most fish and seafood (sea vegetables too!) are cooling to the body and are a great addition to a summer diet.

Besides drinking plenty of water to hydrate your system, In the hot summer months it's wise to the eat foods that can naturally cool the body and keep you from overheating.