Master Gardener: Why bell pepper plants are dropping flowers and fruit

Q: My bell pepper plants have been growing well, and have set many fruits that are now almost full-sized. Lately, I’ve noticed that the flowers and tiny newly-set fruits have been dropping off. Can you suggest a possible cause?
A: I hear this complaint frequently so I’ll cover it more generally possibly to help others who might have similar situations.
My references list boron deficiency, extreme temperature and excessive nitrogen fertilization as possible causes of fruit d