High temperatures, both day and night, interfere with pollination and fruit set in many vegetables. Snap beans tend to drop their flowers readily under these conditions. Squash has a tendency to produce a large number of male flowers and, consequently, few fruit. Tomatoes and bell peppers set few fruit under hot conditions. Butterbeans will drop flowers, but will set some fruit.
Okra, Southern peas and eggplants, however, will continue to set fruit in summer. Green eggplants do not set as well under high temperatures as the purple ones, but the green ones tend to be less bitter during hot, dry weather. Seeds of green eggplants are not always available, but check out local sources and save seed from mature green fruit.