Drying effects of the heat
That depends how long your plants have been suffering. Plants don’t die from heat exposure, but rather from a lack of water to combat the drying effects of the heat.
(Think walking in the desert without water.)
Plants need moisture to keep the cells in their leaf tissues healthy. If there is no moisture for the plant to take up, the cells will burst and the foliage will start to shrivel and burn in the areas farthest from the root ball (source of water) and work its way towards the center of the plant.
When plants are first stressed, they will show you by wilting. When watered within a few hours of wilting, most plants will perk up and look just fine again. They may be saying a few choice words under their breath at you, but all will be forgiven. But if your plant is shriveled and burned, it means your plant was neglected and you could be facing five to ten for plant homicide.
If the plant is in the ground, water the root ball with your hose. Turn the water so that the hose is only slowly dripping. Water for 1-2 hours or until the root ball looks fully saturated.
In a container, try to soak entire container in a bucket of water until it has fully absorbed enough water and the container is heavy again. Then continue back on a regular watering schedule. Do not fertilize your stressed plant to “help” it recover.
If the plant is still alive, it should show some new growth within 7-14 days. At that point, prune off any dead foliage above where the new growth is appearing. Once you have at least 3 inches of new growth, youmay give it a light feeding.