The key to unlocking this mystery is that you are having hot weather. Blossom drop is caused by too hot of weather or too much nitrogen or letting the plants dry out. In your case I am guessing the hot weather is to blame. Not much you can do about that but once the weather cools you may see some fruit set. Try not to get the foliage wet when you water and feel the soil before watering twice a day. Tomatoes like to dry out a bit between watering so water when the top one inch of soil is dry.  Next year get your plants into the ground sooner so they can set fruit before the weather heats up. Keep growing, Marianne Binetti