If your tomatoes are staying green, not setting new fruit, or the fruit is rotting on the vine, here are some possible causes and cures for the problems. Ordinarily, tomatoes grow and ripen faster as temperatures increase. However, when daytime temperatures exceed 100 F and nighttime temperatures remain in the 80s, the ripening process slows down rather than increases. Pigments simply don't form when temperatures get too high. To hasten the ripening process, harvest the tomatoes when they show the first blush of red color and allow them to finish indoors.
Common belief is that nothing tastes better than a vine-ripened tomato.
Taste tests, however, have shown that there is little noticeable difference between vine ripe and picked-early ripe tomatoes. Pollination doesn't take place and the flowers fall off. Next year try planting some of the new varieties that help combat this problem. Finally, tomatoes can be injured by bright sun and high heat resulting in sun scald. Sun scald starts as a light-yellow, leathery area on the tomato surface.