Most people are not aware that there are many varieties of tomatoes available. Some of them are more tolerant of extreme heat than others. If you live in an area that experiences long periods of heat above 90 degrees F, than you will want to use Heatmaster or Solar Flare varieties. You will produce much more and higher quality fruits with these. They are bred to resist high temperatures.
Dealing With Direct Sunlight:
Shade cloths can be purchased at garden centers that will provide some shade. Different kinds of shade cloths provide more or less shade. They can lower temperatures by over 15 degrees. Most resources recommend that the tomatoes be exposed to the sunlight from the east so they will get the less intense morning sun. Ensure that your plants are covered between the hours of 10 am and 2 pm.
Mulch It Up:
Mulch comes in many different varieties. Most of the time it will be made from a material that is available in the area you live in. Adding a thick layer of mulch around the bases of your plants will help them stay hydrated. I do not think that it is possible to add too much mulch. Ensure that you are changing the mulch a couple of times during the season. It will break down quickly. You must water your tomato plants regularly. I will water them every evening once the sun starts to go down. Some people set up a drip system, I do not have the time or the money for this, so I use a simple plant sprayer.
I look at my plants every single day. They need more water if the soil at the base appears to be cracking. Then I will spend more time watering them in the evening.
Do not allow the fruits to spend too much time on the vine. Inspect each one as it turns red. If it is nice and firm then it is ready to pick. Inspect each one of your plants every single day. I inspect my plants twice daily during peak season. If you live in an area where mid summer temperatures top 90 degrees you might have to pick orange tomatoes. They will stop turning red once the intense heat begins. Pick the fruit that is turning a bit orange and allow it to turn red inside where it is cooler.
Many people believe that you cannot grow great tasting tomatoes way down south. I don't believe this. I have given you a few tips here to make your growing season a successful one.