This goes both ways – Too little because we forgot to water when the heat was forecast, so plants were depleted perhaps so much that they’ll not recover even with deep watering now. Too much because we watered heavily during the onslaught, perhaps drowning the roots and activating phytophthora organisms resulting in rotting roots. Just remove old tomato foliage at the bottom of the plant that's turned pale and brown; healthy growth above will take over.
Sunburned foliage, branches, and fruits.
If there isn’t enough foliage to cover the branches and trunk of plants or trees for most of the day – especially the late afternoon when the sun is the most intense - they may have sunburned, which may lead to bark falling off and pests boring in. This is possible during the winter as well, especially on deciduous fruit trees – which is why I paint a 50% mixture of inexpensive light-colored indoor water-soluble latex paint on my east- , south-, and west-facing branch and trunk surfaces to reflect the sun. While it seems counterintuitive to use indoor paint on outdoor trees, using oil-based outdoor paint would smother the tree’s pores!
Pest onslaught, especially of red spider mites.
Pests that love the heat will take advantage of weakened plants. Spider mite damage looks like tiny stippling on greenish-yellow or yellowish-white foliage (which should have been a rich green), and tomatoes are a favorite.
Delay in new bloom set.
Blossoms set well on healthy plants in air temperatures between 55-85 degrees. Above and below that range, the blossoms stop. Additionally, they won’t again resume setting new blossoms until that 85-degree or under has been the case for a full two weeks – so it may be a month or more before we get more blossoms. This is why it’s important for us to get our tomato plants healthy and developed as soon as possible in the spring, so we get a great blossom and fruit set before the above-85-degree heat settles in!
This is really an issue of timing of harvest and refrigeration after harvest. It’s based on cell structure. If you plan to refrigerate fruit – whether tomatoes or melons or peaches or whatever – harvest them when the air temperature is as cool as possible – ideally 4 hours before sunrise; then refrigerate them immediately. This means that the cells will not have much change in temperature, so the fruit will last longer in good condition (although some flavor quality will be lost due to refrigeration). On the other hand, if the fruit is hot when you harvest it, and then you refrigerate it immediately, the change in temperature is too extreme and cell structure breaks down so the resulting texture is mushy. So, if you want the premium development of flavor and will enjoy the fruit within a couple of days, harvest in the early evening and store on the countertop on a rack with air between each piece of fruit. And, place each piece as if it was still attached to the tree or plant: tomatoes and figs with the stems upright, and melons with the stem separation pointing to the side.