Answer: It doesn't sound as though the flowers are being pollinated. You can try tapping the branches with open flowers to coax the pollen to fall down from the male to the female parts of the flower. When temperatures are hot (over 90F), the pollen can become sterile and no pollination will take place. Since you can't control the temperatures, you may want to plan on planting tomatoes a bit earlier in the year so you can harvest the fruit before August when the weather is really hot.
Wish I had more suggestions!
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