Answer: Research shows that most tomato varieties don't set fruit well when nighttime temperatures are above 70 degrees or daytime temperatures are above 90 degrees. Tomatoes seem to be most sensitive to temperature extremes at night. Temperatures between 59 degrees and 68 degrees provide the best conditions. Above or below these temperatures, fruit set is reduced or nonexistent. This is because the pollen is rendered sterile in extreme heat. There are some heat tolerant tomatoes, if you live in an area of extreme temperatures. If so, try growing Equinox, Heatwave, Solar Set, Sunleaper or Sunmaster.
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