I am expecting this has to do with the outside temps which are touching 90F and the plants have not been under shade.

The only thing that has got me a bit worried is that even when the temps were going above 95F sometimes back, they looked fine then. But after the flowers have bloomed, this has happened / is happening.

Is this a phenomenon that starts after flowering, when temps rise above certain levels? Perhaps because of the flowering stress.

On a side note, the flowers are also not forming fruit and dropping. I understand the temps may have a large part to play in this as well.

What can I do overcome these two things?

Perhaps your plants have more leaves and are bigger now and the leaves are losing moisture faster than the roots can take it in. I am not a botanist so that may not be what happens. I know many plants wilt in the hot parts of the day even though they don't need water and will recover when it cools off in the evening.

I am not familiar with your climate. Tomato growers in hot climates here try to grow tomatoes early in spring and get their production before the worst heat of the summer. People in different climates have to adjust in many ways to get a crop at the best possible time. Perhaps your university has information about the best varieties and best times there.