Hot weather stand bys are, potato salad, 5 bean salad, romaine lettuce salad, tuna salad, deviled eggs, fruit salad and hot dogs and hamburgers on the grill.
If the weather is real hot I try to have cold snacks like melon sliced up and in my roasting pan in the fridge, bananas cut in half with a a stick inserted, dipped in melted chocolate and frozen on a tray in the freezer. Sometimes it's just too hot for a big meal.