The color of your tomatoes can be affected by high temperatures. Red pigments don’t form properly when temperatures rise above 95 degrees F. The orange and yellow pigments are not similarly affected. The result is often orange-colored tomatoes rather than the usual “tomato red”. There is no reduction in the edibility or taste of the orange tomatoes. Since tomatoes will ripen fully even though they have been removed from the vine once they begin to show color at their base, you can have nice red tomatoes despite high temperatures if you pick them when they begin to show color and let then fully ripen in the house.
High temperatures also affect the number of tomatoes that are produced. This is because temperatures that remain above 75 degrees F at night and day temperatures above 95 degrees F generally cause poor fruit set on tomatoes. It is believed that the high temperatures interfere with pollen viability resulting in a lack of pollination. Once cooler temperatures return flowers will continue to set fruit.