Three days of strong sunshine have shown which of my plants are tolerant to high temperatures and which ones aren't.
Leaves are the main indicator of how plants feel and leaf curl, cupped or rolled, and wilting is what tomato plants do when they can't stand the heat on their leaves. Sometimes they even point their leaves away from the sunlight towards the shade!
You can tell if your leaves are being stressed by too much sun if the leaves at the front of the plant are more affected than the leaves at the back. Also the new growth at the top often turns downwards and looks shrivelled.
A way to help the situation is to mist leaves in morning and evening. This also helps with pollination which is more difficult if the air is very hot and dry.
Some varieties originate from places like Siberia so they would be quite happy with cooler temperatures and less sunshine. It is these varieties that are most vulnerable to excess heat and light ... just ask my Black Cherry plants!