The most frequent cause of tomato blossom drop is temperature.
•High daytime temperatures (above 85 F / 29 C)
•High Nighttime Temperatures (Below 70 / 21 C)
•Low Nighttime Temperatures (Below 55 / 13 C)
William, Thanks! It is probably the low temperature at night. There is a person who has a personal weather station that lives close enough I can see their house from mine. I can check temperature from his site. The high temperature for July was 94F and the low was 41F. Last night it got down to 43F. I don’t think there was a day this month with the low temp at night above 55F. Only a few nights where the low got to the low 50’s and the rest was in the 40’s. I sprayed tomato and squash flowers with blossom set spray today and will watch to see if that helps.