You never know ahead of time what type of summer you are going to have. Had we known we would have record breaking heat and drought we would have done a heat tolerant tomato variety trial. But, last year we had unusually cool and wet, so who knew? Our temperatures rose into the 90's and 100's in late June, and did not drop down into the 80's until very late August. Nights were mostly in the 70's. We were hot, and so were are tomatoes.
Of the 60 or so tomato varieties we grew, these were the stand-outs: Juan Flamme, Homestead, Anna Russian, Nyagous, Thai Pink Egg, Sun Gold F1, Super Sweet 100 F1, Juliet F1, White Beauty, Speckled Roman, Rose de Berne, Black Cherry, and Green Grape.
These did okay, and were worth growing: Abraham Lincoln, Legend, Orange Banana, Speckled Roman, Black Zebra, Arkansas Traveler, and Amish Paste.
And here is the list of "don't bother" if you have hot, hot summers: Ananas Noire (We have not harvested one single fruit!), Reisentraube, Isis Candy, Marmande, Old German, Pineapple, Bush Beefsteak, and Prairie Fire. Some of these grow exceptionally well where summers are moderate, but don't grow 'em in Texas!