Not a vegetarian myself, but my girls and I make this frequently in the summer. (And 90 sounds awesome, our high today is supposed to be 121℉)
Mix 1 or 2 chopped tomatoes, a small avocado, 1cup of corn ("roasted" in a dry skillet till it has brown spots), a can of black beans drained and rinsed, an some chopped onion. Drizzle with olive oil and lime juice. Salt and pepper to taste. Good with tortilla chips, a quesadilla, on a baked potato, or I just eat with a spoon sometimes. Low prep and a cool, refreshing meal. Complete protein too.